Serve statistics – Heavy Topspin

The Second-Serve Woes of Arthur Fils

*The outcome of this point depends a great deal on whether Arthur Fils is about to hit a first or second serve.*

Arthur Fils is a bit of a forgotten prospect. A year younger than Carlos Alcaraz and two years older than Joao Fonseca, he isn’t considered to have the awe-inspiring talent of either. Then again, who does? By any other standard, the 20-year-old Frenchman has made tremendous progress. Standing at #19 on the ATP computer, he’s the top-ranked player under 21, and he’s even within the top five of under-23s.

There’s no secret to the Fils game. He hits hard, smacking serves over 130 miles per hour and occasionally connecting with a forehand that might even cause Fonseca’s eyebrow to twitch. In Saturday’s Davis Cup match against Thiago Seyboth Wild, he scored 11 aces in only 54 service points. He won 29 of 32 points when he landed his first serve.

The Frenchman has plenty more to his game, as well. He is sturdy off both wings, unafraid to battle from the baseline. He rates +5 in Forehand Potency, hardly a tour-leading number, but better than the likes of Daniil Medvedev and Holger Rune. By the same metric, his backhand is neutral. That’s another number that looks better in context: He won’t win any awards, but the shot isn’t holding him back.

At first glance, then, his biggest challenge is making inroads on return. He has won 36.2% of return points over the last 52 weeks, a number just below the usual minimum for an elite player. It ranks him above Rune, Hubert Hurkacz, and Taylor Fritz, but behind most of his fellow top-20 players. It isn’t an obstacle to cracking the top ten, though, as Hurkacz and Fritz have shown.

Fils’s problem now is what happens when he misses that big first serve. Among the ATP top 50, he ranks 16th in first-serve points won, just ahead of Karen Khachanov. By second-serve points won, he ranks a dire 43rd, several places down the list from Sebastian Baez. Even in Saturday’s Davis Cup rout, the Frenchman failed to win half of his second-serve points.

What’s going wrong? Is it something that young players tend to improve? What does a second-serve weak point say about a prospect’s future trajectory?

Second to many

Let’s get a sense of the typical relationship between first- and second-serve win rates. This scatterplot shows the ATP top 50 over the last 52 weeks:

Players who are successful behind one serve are generally successful behind both, with Jannik Sinner leading the way in the upper-right corner. Carlos Alcaraz and Novak Djokovic rank among the second-serve win rate leaders, though their first-serve results aren’t as strong. Grigor Dimitrov and Giovanni Mpetshi Perricard pop out as men with effective first serves who don’t do as much behind the second.

Fils hardly sticks out as a disaster, especially with Alexander Bublik there to distract us. Still, for a man who can win more than three-quarters of his first-serve points, he sits in the wrong part of this grid. There’s virtually no difference between his and Ben Shelton’s first-serve results, yet the American wins five percentage points more often with his second serves. Shelton is top-five in hold percentage, while Fils languishes outside the top 30, despite a near-identical first-serve success rate.

The diagnosis

It’s one thing to say that a player doesn’t win enough points behind his second serve. Can we figure out why?

Start with two things it’s not. Fils commits more double faults than average: 4.1% of serve points versus the typical top-50 rate of 3.4%. But even when he lands his second serve, the results are disappointing. Instead of 43rd among the top 50, he’s 37th. Fewer doubles might be nice, but they would barely move the needle.

We can also cross particularly soft second serves off the list. At the US Open last year, Fils averaged 115 miles per hour on first serves and 92 miles per hour on seconds. That’s a gap of 23 miles per hour–exactly in line with the norm among players who reached the third round. Jannik Sinner averaged 91 miles per hour with his second serves, so raw speed isn’t the problem.

That leaves us with where the second serves are landing. Unscientifically, I get the impression that Fils’s second serves don’t land particularly deep. Khachanov, for instance, hits a bog-standard topspin second, yet it’s fine because he consistently drops it deep in the backhand corner. The Frenchman sometimes hits that serve, but just as often his not-enough-topspin delivery lands in the middle of the box. In 2025, against this field, that’s not going to cut it.

Match Charting Project data can’t tell us how deep the serves are landing, but it does tell us what direction they go:

           Dc-Wide  Dc-Body   Dc-T   Ad-T  Ad-Body  Ad-Wide  
Fils 2nds    17.5%    38.1%  44.4%  11.3%    20.4%    68.3%

First, the Frenchman rarely goes for the forehand. With a really good second serve, that’s smart. But with less imposing strikes, it gives opponents options. Last week I linked to an analysis of Alcaraz’s loss to Djokovic in Melbourne, where Alcaraz went to the backhand side on second after second–probably too often. That gave Novak the flexibility to position himself differently and play the returns more aggressively. Fils is making a similar offer to everyone he plays, especially on the ad side.

Second, that’s a lot of deuce court serves down the middle. “Body” is misleading–usually when we talk about body serves, we mean the really good ones, flying 125 miles per hour at the returner’s left hip. That’s not what’s happening here. A more appropriate name for the category is something less inspiring, like “serves that aren’t in a corner.” Whether the returner has move a couple steps or none at all, those are booming forehand returns waiting to happen.

Here are the directional breakdowns of a few men with strong second-serve results, for comparison:

           Dc-Wide  Dc-Body   Dc-T   Ad-T  Ad-Body  Ad-Wide  
Fils         17.5%    38.1%  44.4%  11.3%    20.4%    68.3%  
Shelton      27.3%    40.3%  32.4%  21.6%    35.0%    43.4%  
Djokovic     35.5%    38.8%  25.6%  30.6%    27.2%    42.2%  
Sinner       14.1%    61.5%  24.4%  15.0%    49.8%    35.1%

Both Shelton and Djokovic mix things up a lot more. Sinner does everything I’ve just criticized about Fils and, at least in New York last fall, he did it at the same speed. Sheepish grin emoji. Surely there’s more going on there, but we’ll have to save it for another day.

In development

In one way, clear weaknesses are a good thing. It’s easier to identify a clear target area for practice than to vaguely aim to get a little better at everything. I’m sure Fils and his team are aware that he should get more out of his second serve, and we’ll see him change things up.

The question, then, is if those efforts are likely to bear fruit. Many players struggle to meaningfully improve their stats once they’ve established themselves on tour. It’s hard enough to tread water. Opponents figure out how to counteract their weapons, age and wear-and-tear take their toll, and–if the player is lucky enough to climb the rankings–the average opponent in later rounds is stronger.

Fils has compared himself to Jo-Wilfried Tsonga. Tsonga never had a sub-50% second-serve win rate, but he did have middling figures around 51.5% in his first two years on tour. On the other hand, Tsonga was a late bloomer: He was barely playing Challengers when he was 20.

For a more comprehensive answer, I found 75 men who played full seasons on tour at age 20 since 1991. All but five of them eventually bettered their age-20 second-serve win rate, and the average improvement was 2.7 percentage points. If that holds true for Fils, he’ll peak around 52% on second serves. That’s not bad, though I suspect he would be disappointed if he never does better than that. It would still be an underperformance for someone with his first-strike weapons.

Indeed, the one-third of these players who posted sub-50% second-serve win rates at age 20 improved more than the larger population. They gained 3.4 percentage points. Among them are some names that might inspire even greater feats from the young Frenchman:

Player           Age 20 2ndW%  Peak  Peak 2ndW%    
Andrey Rublev           49.3%  2020       53.9%    
Nicolas Almagro         49.1%  2012       55.1%    
Sam Querrey             48.2%  2015       54.1%    
Tommy Haas              47.7%  2006       54.8%

All four won fewer second-serve points at age 20 than Fils did in 2024. Each one fully shored up the weakness– at least for one season. 54% isn’t elite, but it’s more than good enough, especially when paired with a top-notch first serve.

To be clear, I’m not forecasting a Haas-like, seven-point improvement for Fils. Repairing weak points at tour level is exceptionally difficult, and even the three-percentage-point norm will take a lot of work. It is nonetheless a challenge the Frenchman will need to undertake. He has come a long way on the back of a big first serve, but to breach the top ten, he’ll need a more well-rounded attack.

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The Locked-Down Serve of Jannik Sinner

*It’s all business for Jannik Sinner, and business is good.*

There are a lot of things we could talk about after Jannik Sinner’s latest display of dominance. With a second Australian Open title, his exceptional span of hard court performance has stretched to 13 months, and according to my Elo ratings, only eight players in the Open era have ever been better than the Italian is right now.

A year ago, I wrote that Yes, Jannik Sinner Is This Good. If anything, he has improved since then. He holds serve more often than anyone on tour–yes, even more than Giovanni Mpetshi Perricard. Yet he is far from one-dimensional. He couples the serve with elite groundstrokes on both wings. He breaks serve more often than all but six players on the circuit.

One particular aspect of Sunday’s victory stands out. In three sets, spanning 15 service games, Sinner did not face a single break point.

Zero break points faced is one of those stats that sounds really good–then it gets even better the closer you look. Alexander Zverev a top-ten returner. He breaks nearly one-quarter of his opponents’ service games. He earns approximately 0.6 break points per game, or three per set. In three sets, the Italian didn’t allow him one.

Every season there are a couple hundred matches in which the winner doesn’t face a break point. Yet most of those are short best-of-threes, many of them involving overmatched wild cards and qualifiers. In 2024, there were only five matches in which a top-ten player failed to generate a single break point over more than ten return games. Twice the victim was Hubert Hurkacz, probably the weakest returner among the elites. Another hapless outing came from Casper Ruud, who was held to zero by Zverev at the Tour Finals.

The other two standout matches belong to Sinner. In last year’s Australian Open semi-final, then again in the Shanghai title match, he shut down Novak Djokovic. The only recent precedents for Sinner’s plastering of Zverev are the Italian’s own performances.

What can we learn from the latest episode of the Sinner show?

Situational awareness

Twelve months ago, Sinner was developing a reputation as an escape artist. He beat Daniil Medvedev in a five-set Melbourne final, winning just one more point than the Russian. He snuck past Djokovic twice in November 2023, once winning exactly the same number of points, a second time despite winning four points fewer.

Sinner had a knack for erasing break points. Most players are less successful facing break point than on other service points, because stronger returners generate more break points. (Also, break points tend to crop up amid rough patches, at least for players human enough to occasionally slump.) The Italian, though, saved break points at a better clip than his other service points. He hit bigger at those moments, and it worked.

Recognizing that trend a year ago, I tempered the celebration with a dose of reality:

…I can tell you what usually happens after a season of break-point overperformance: It doesn’t last. Taking over 2,600 player-seasons since 1991, 582 (21.7%) of players saved more break points than they won serve points overall. 183 (6.8%) matched Sinner’s mark of saving at least two percentage points more than their serve-points-won rate.

That sound you hear? That’s Darren Cahill laughing at us. Sinner didn’t quite continue at the same pace, but he still serves better facing break point than otherwise. He wins a tour-leading 71.5% of serve points overall, and the number climbs to 72.5% when an opponent has him on the ropes.

(71.5% is circuit-best, but 72.5% is not: Ben Shelton stands at 73.1%. No one told Jannik, though. In their semi-final, Sinner won 6 of 13 break points against the Shelton serve.)

Of course, this specific skill didn’t come into play on Sunday. Sinner didn’t have break-point-faced results, because he didn’t face any break points. If you have an even bigger weapon to deploy at key moments, why wait until it’s absolutely necessary?

Beyond the escape room

Some players–especially left-handers–are more effective serving to the ad court than the deuce court. That helps them save break points, because most break points (30-40 and ad-out) take place in the ad court.

Sinner is right-handed. Across the 250-plus matches for which I have sequential point-by-point data, he is slightly more effective serving to the deuce court:

COURT    A%   SPW%  
Deuce  7.6%  66.6%  
Ad     6.5%  66.3%

The different in points won isn’t anything to build a strategy around, but the ace-rate gap suggests there might be a meaningful difference.

In Melbourne, the success rates took on a new look. Based on the five Australian Open matches in the Match Charting Project database, here are the same metrics:

COURT    A%   SPW%  
Deuce  8.9%  74.6%  
Ad     9.4%  70.8%

The ace rates flipped, but holy four percentage points! 70.8% serve points won is very good, better than anyone else on tour over the last 52 weeks. 74.6%, though: That’s from another planet. It’s better than John Isner’s best season.

It may be a fluke. After all, it’s just five matches, and Sinner’s deuce- and ad-court results were nearly identical in 2024. But I suspect there’s strategy at work here.

Up to eleven

I noted last year that Sinner served bigger facing break point than he did otherwise: 125 miles per hour compared to 122. What about other key situations?

At the US Open last year, the Italian showed some deuce-court preference, winning 72.7% of deuce-court points compared to 71.3% on the ad side. It wasn’t a matter of power, as he averaged almost identical speeds (117.9 to 117.7 mph) in the two directions.

Speed differences turn up at a more granular level. Here are Sinner’s first-serve speeds at the most common point scores he faced:

Score    MPH  
15-30  121.0  
40-40  120.3  
40-15  120.0  
0-15   119.7  
30-30  119.4  
40-30  118.0  
30-15  117.7  
30-0   117.0  
15-0   116.6  
0-0    116.6  
15-15  115.8  
40-0   113.0

(Yes, I know it’d be nice to have 30-40, 40-AD, 15-40, and so on. But this is Sinner we’re talking about. He didn’t face many of those.)

With the exception of 40-15, this list is an awfully good approximation of point scores listed by importance. With more at stake, the Italian hit harder. There’s no apparent trade-off, either. He made more first serves than average at 15-30 and deuce, even with the faster strikes.

The point is that when Sinner feels the need to go big, he has the ability to do so. Most players don’t: Their results don’t get better in critical moments, either because they’re already maxing out their skills on routine points, or because their opponents can raise their levels, as well. But the Australian Open champ has more in the tank than anybody who dares to stand across the net from him.

As the Italian rose through the rankings, he saved that extra oomph for break point. Now that he enters every match as the favorite, he can be even more aggressive. By serving harder at 15-30, or 30-all, Sinner probably doesn’t risk overexposure. With the possible exception of Alcaraz or a time-traveling Djokovic, no one can do much with an accelerated Sinner first serve–even if they’ve seen one recently.

The full arsenal

Put all of this together, and it’s hard to avoid the conclusion that Sinner will continue to climb the all-time list. In terms of peak level, Andy Murray is next:

Rank  Player          Peak Elo  
1     Bjorn Borg          2473  
2     Novak Djokovic      2470  
3     John McEnroe        2442  
4     Ivan Lendl          2402  
5     Roger Federer       2382  
6     Rafael Nadal        2370  
7     Jimmy Connors       2364  
8     Andy Murray         2347  
9     Jannik Sinner       2325  
10    Boris Becker        2320

Sinner wins more service points than anyone else in the game–even when he isn’t particularly trying. At the same time, he is an elite returner.

We’ve seen a few players with a similar service profile. Pete Sampras also had a knack for coming through at the end of sets. But he leaned on his tiebreak skill more than Sinner ever will, because his return game was mediocre. Roger Federer was better: a dominant–and clutch–server, and a more competitive returner than Pistol Pete. Nick Kyrgios had one of the most electric serves in the game’s history, coupled with the ability to focus at critical moments. Yet he was the most one-dimensional of the bunch. His return would have held him back even if he had stayed healthy.

Sinner has all the serve dominance without the drawbacks. He has no apparent weakness. He won’t win all the time, and he won’t stay on top forever, but at the moment, it’s hard to see how anyone will stop him.

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Elina Svitolina Plays Hard

*Elina Svitolina at the 2020 Australian Open. Credit: Rob Keating*

Here’s a stat to get us rolling: In yesterday’s fourth round match at the the Australian Open, Elina Svitolina won 67% of points when she hit a backhand. Tour average is a neutral-as-its-gets 50%. Svitolina, with her resourcefulness off that wing, averages 51%.

It gets even better. Usually, if a rally statistic comes out much above 50%, it’s because it’s loaded with winners. But against Veronika Kudermetova yesterday, Svitolina hit just one backhand groundstroke winner. She induced two more forced errors, but committed five unforced errors of her own. All of which is to say, those point-winning backhands came thanks to point construction, not swinging for the fences. (An erratic Kudermetova helped, too.)

The backhand masterclass, on the heels of another strong baseline performance against Jasmine Paolini in the third round, recalls Svitolina’s peak. The Ukrainian is now 30 years old, veteran of innumerable injuries, a pregnancy, and the perpetual distraction of her country at war. My Elo ratings suggest that she was at her best nearly seven years ago, after she upset Simona Halep for the the 2018 Rome crown. That’s an eon in tennis time: She hasn’t held a place in the top ten since 2021.

Yet here she is, in the Melbourne final eight. It’s her twelfth major quarter-final, her fourth since becoming a mother. She might have made it one more a year ago. After a grueling runner-up finish in Auckland to open her 2024 campaign, Svitolina raced through three rounds at the Australian before retiring to Linda Noskova in the fourth round. This year, she skipped the warmups and has sustained her best tennis on the bigger stage. With Madison Keys across the net tomorrow, she has a chance to go even further.

Svitolina 2.0 will probably never reach the level she showed in the mid-2010s. She’s a half-step slower, and she needs to manage her schedule with care. But like all players with successful second chapters, she has changed her game in response to her limitations. She is, and always will be, a counterpuncher, leaning on one of the game’s sturdiest backhands. Yet the new Elina has first-strike weapons that her younger self could only dream of.

Hitting big

While no one is about to mistake her for Aryna Sabalenka at the service line, the 30-year-old does more damage than she used to.

Yesterday against Kudermetova, Svitolina averaged almost 103 miles per hour (165 kph) on her first serves. I have first-serve speed for more than 70 of her career slam matches, and she hit that level in only five of them, mostly at Wimbledon. When she reached the quarters at the 2021 US Open, she averaged less than 100 miles per hour in all five matches.

It’s a small improvement, but coupled with increased precision on the first serve, it is paying off. In the sample of Match Charting Project-logged matches, she converted more plus-ones behind her first serve in 2024 than her career rates. Even her improved 2024 marks pale in comparison to what she has done in Melbourne:

Span               Unret%  <=3 W%  
Career              27.2%   38.6%  
2024                27.5%   41.9%  
R3 vs Paolini       36.1%   60.6%  
R4 vs Kudermetova   39.4%   63.9%

The second column, showing the percent of first-serve points in which Svitolina won the point with her serve or second shot, is where players make their money. No matter how good your ground game, it's tough to make up a deficit in the cheap-points category. Through 2024, the Ukrainian was middle-of-the-pack in both of the stats. The form she has shown in the last few days is something entirely different.

The numbers are particularly impressive against a defender like Paolini. While the Italian probably isn't as strong as her #4 ranking suggests, she is certainly an elite returner. In charted matches last year, she put nearly three-quarters of first serves back in play. Svitolina allowed her only 64%. And as we see with the serve-or-second-shot stat, Paolini couldn't do much when she did get the ball back. On average, the Italian wins more than half of the first-serve points in which she lands her return. On Friday, she won just 6 of 23.

There's just one reservation about the third-round performance. Svitolina got those results by taking chances, and she made fewer than half of her first serves. It was a day of extremes: 48% of first serves in, 83% of first-serve points won, and 42% of second-serve points won. Had she explicitly targeted a more typical 60% rate of first serves in, she wouldn't have posted the same win rates. But with a first-class returner across the net, Svitolina's tactics were proven correct.

That half step

So far we've talked about what the Ukrainian can control. Just as important is what she can't: The aging process and its effect on the rest of her game.

Here's an overview of how her current level compares to her 2017-20 peak, measured by first-serve and second-serve win percentages, along with return points won:

Span     1st W%  2nd W%   RPW%  
2017-20   66.6%   47.2%  46.1%  
2023-25   65.5%   46.8%  45.2%

Approximately a one-percentage-point drop across the board. That makes sense as an explanation of the difference between a player ranked around #5 and one who should be hovering around #20. (Elo is more optimistic than Elina's official ranking of #27.)

Now try the same stats, hard courts only:

Span     1st W%  2nd W%   RPW%  
2017-20   67.5%   47.3%  46.1%  
2023-25   68.9%   47.9%  43.6%

At her peak, Svitolina was basically the same player on all surfaces. Now, she sports a different type of surface profile. The service aggression is paying off, while she seems to be struggling to do return damage on faster courts.

The 30-year-old has always aimed to get a lot of serves back. According to MCP data, she has put 77.5% of serves in play, a number that fell to 76.4% last season. Both marks are near the top of the table. Players who adopt such a defensive posture usually don't win a particularly high rate of those points, and Svitolina is no exception: Her 51.5% win rate when she puts the return in play is roughly tour average. It's a low-risk, fairly-low-reward strategy.

Against strong servers, the results can be bleak. She got fewer than 65% of serves back against Sabalenka in Cincinnati last summer, and even Ons Jabeur held her to 67% at Wimbledon. In Adelaide three years ago, Madison Keys was so strong from the line that Svitolina put only half of returns in play. At her peak, it was rare for the Ukrainian to fall below 70%.

Her hard-court results, then, depend a great deal on the matchup. The relatively punchless Paolini was a lucky draw in this regard. Once the serve and the plus-one are past, Svitolina can go toe-to-toe with anybody. She won 60% of points that lasted four or more strokes against the Italian. Facing Kudermetova, as we've seen, it was even easier. Once Elina got her racket on a backhand, the Russian basically gave up.

It's a mad, mad quarter-final

Svitolina's next challenge is entirely different. In five career meetings, she has two victories against Keys, coming at the Australian Open and US Open in 2019. Even when she was younger, she couldn't neutralize the American's serve. She has won about 36.5% of return points in their head-to-head, never topping 43.3% in a single match.

The margins for the Ukrainian tomorrow will be slim. While Svitolina has boosted her serve, she has gained more plus-one points than unreturned serves. That works against opponents like Paolini, but Keys swings big at everything, including hard serves. In the Adelaide final against Jessica Pegula--a broadly similar player to Svitolina--Keys held her opponent's serve points to an average of 3.1 strokes. That's a lot of short "rallies," and it means fewer chances for Elina to put away a weak second ball.

Svitolina will find herself even more powerless on return. As we've seen, Keys is responsible for one of the worst performances of her career. In that 2022 Adelaide match, the 30-year-old won a miserable 22% of return points. The longer the rally, the better for Svitolina. But Keys will try to prevent the commentators from using the word "rally" at all. In the Adelaide title match, the American's service points lasted, on average, a mere 2.6 strokes.

The Ukrainian may not have much control over the proceedings, but that isn't to say she doesn't have a chance. My forecast leaves her plenty of room, giving her a 42.5% shot at reaching the final four. Keys's aggression often goes astray, and nagging injuries could hamper either player. If the American can't serve at 100%, or if she falls back on more passive tactics, the underdog will pounce. In longer points, Svitolina is the clear favorite. She'll have to hope she gets the chance to play some.

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This Is What a Dangerous Madison Keys Looks Like

*Madison Keys in 2023. Credit: Hameltion*

Last year, Madison Keys missed the Australian Open with a shoulder injury. She ended up playing barely half the season, missing more time after tearing a hamstring at Wimbledon. She still won enough matches to head to Melbourne as the 19th seed at this year’s first major.

She’s better than that.

In one sense, I’m just stating the obvious: She beat Jessica Pegula for the title in Adelaide on Saturday and moved up to 14th on the WTA computer. Beyond that, anyone who can hold on to a spot in the top 20 despite missing so many events is probably better than their ranking. Elo agrees, rating Keys ninth among women, a modest 33 points behind fifth-place Elena Rybakina.

Even more striking is the way the American won the Adelaide championship. She served as well as she has in years, indicating that the shoulder is fully healed. She played extremely aggressively, a style that she has never shied away from, but that she sometimes struggles to maintain. Finally, Keys did all that while posting excellent return numbers. The 29-year-old is a two-time semi-finalist at the Australian Open, and if she keeps this up, she could easily make it three.

The serve is back

When everything clicks, no one on tour–with the possible exception of Rybakina or Aryna Sabalenka–makes serving look so easy. Keys doesn’t just slam flat serves down the tee: She adds a bit of side spin, so her inch-perfect deliveries look like they’re sailing slightly wide until after they cross the net. Then she employs the same spin to send wide serves even wider. When she misses, she can fall back on some of the heaviest topspin seconds in the women’s game.

Whether the shoulder was still shaky or the hamstring compromised her motion, the American struggled to maximize her serve as late as last year’s US Open. In her third-round loss to Elise Mertens, her average first-serve speed was just under 99 miles per hour. Out of nearly 100 grand slam matches for which I have serve speed data, it was only the second time–the other was 2017 Roland Garros–that she hit firsts so slowly.

Today in her Melbourne opener against Ann Li, her average first serve was 109 miles per hour. That’s the fastest I have on record for her since 2015.

I don’t have serve speeds for Keys’s victories last week in Adelaide, but the results hint at numbers well into triple digits. In the final against Pegula, she hit 10 aces, good for 13% of her serve points. Facing Liudmila Samsonova in the semis, she smacked 12 aces–17% of serve points. In a short quarter-final against Daria Kasatkina, she tallied 11 aces, an eye-popping 21% of serve points. It was only the fourth time in the 2020s that Keys topped the 20% mark and the only time in her career she managed it against a top-ten opponent.

Adelaide marked the first time since 2019 that the American aced at least 10% of her service points in three consecutive matches. She hadn’t done so at a single event since 2016.

Aces are great in themselves, but the stat is particularly useful for representing the serve’s effect on even more points. Yes, Keys won 13% of her serve points against Pegula with aces, but 41% didn’t come back. That’s another sign of a revival: In dozens of Match Charting Project-logged matches, it’s the first time she’s topped 40% in that category since the Australian Open in 2022–her most recent semi-final run Down Under.

The American mitigated her shoulder woes last year by starting points more conservatively. She wasn’t as deadly with her first serve, but she landed more of them. Among the WTA top 50, only Elina Avanesyan and Yulia Putintseva missed fewer first serves. If Adelaide is any indication, it’s back to business as usual, taking a few more risks and wreaking absolute first-serve devastation:

Span        SPW  1stIn  1st W%  2nd W%  
Adelaide  65.4%  63.4%   71.6%   54.8%  
2024      60.6%  68.2%   66.7%   47.4%

It’s not an apples-to-apples comparison, because the 2024 line contains plenty of clay-court matches, including two against Iga Swiatek. But the difference is sufficient to tell the story anyway. 60.6% of serve points won was good for 8th-best on tour last year. 65.4%, on the other hand, is almost two percentage points better than anyone posted on hard courts. The 71.6% first-serve win rate would have put her in the top five, and no one came close to winning 54.8% of their second serves.

I don’t want to put too much emphasis on a single tournament–everybody looks good if you turn the microscope on a great week. But it’s worth offering one more tidbit in Keys’s favor. She posted those numbers against extremely strong opposition. Her five victims in Adelaide were ranked 16th, 17th, 9th, 26th, and 7th, respectively. That’s a tougher schedule that any player faces over the course of an entire season. If Madison does reached the Melbourne semis, it’ll be an easier path than she faced to collect the trophy in Adelaide.

Swinging freely

Keys has improved her return game over the years, and she’s gotten more comfortable playing long rallies. One of the more surprising numbers on her stat sheet is that she has a better winning percentage on clay than on hard courts.

Still, she’s an aggressor at heart. Her serve isn’t the only shot she can hit as hard as anyone, nor is it the only weapon she can land on the line. Generally speaking, the more aggressive she is, the better her results. The shoulder and hamstring injuries forced her to play more conservatively. That is now over.

In less than an hour on court with Kasatkina, she crushed, by one count, 38 winners. Facing Pegula on Saturday, she tallied 40. I have winners and unforced errors for about one-quarter of her career matches, and the Adelaide final was the first time she cracked 40 winners since 2019. It wasn’t uncontrolled either. The opposite side of the ledger was a respectable 27 unforced errors, good for a ratio of 1.5. Even in her Auckland loss to Clara Tauson the previous week, she recorded 38 winners against 30 unforced, a ratio that would win most WTA matches.

The best indicators of the American’s renewed attack are the various metrics for aggression. By Rally Aggression Score–a measure of how often a player ends points for good or ill after the return of serve–she rated +147. (Average is 0, and almost all players fall between -100 and 100.) Return Aggression Score–the same idea, but strictly for returns of serve–put her at +137. Her career averages are around +100, but in 2024, she fell below +60 in both.

The last time that Keys reached +137 or higher by both measures was the 2019 Cincinnati quarter-final, when she beat Venus Williams en route to the title.

We keep finding things that Keys has done for the first time since 2019. They almost all go back to that week in Cincinnati. (Coincidentally, she straight-setted Kasatkina there, too.) With the possible exception of her 2017 US Open final run, the Cincinnati effort was the best of her career. She has found that form again.

Keys to the match

One difference between 2019 Cincinnati and 2025 Adelaide: The American returned a whole lot better last week. She won 48.1% of return points in Adelaide, compared to 43.7% in Cinci.

It’s rare for players to substantially improve their return game once they arrive on tour. The rest of the tour learns how to beat you, the opposition gets stronger, and age slows you down. Yet Keys, in her late 20s, has gotten better:

While the 2025 data point probably won’t stick above 47%, the 2023 and 2024 results demonstrate the trend. Last year, Keys’s 44% mark was better than half of the top 50, a strong showing for a serve-first player. Return points are an extreme case of tennis’s small margins. By top-50 standards, 43% of return points is weak, 44% is adequate, and 45% is strong.

47%–the American’s success rate in Auckland and Adelaide–is beyond elite. Only two players–Coco Gauff and Marketa Vondrousova–did better than that on hard courts last year.

It will take some time before we know whether Adelaide was an outlier or a harbinger of a resurrected career. Keys’s 2025 season will surely fall somewhere in the middle, at least if she remains healthy. There are certainly reasons for optimism. For the most part, she’s done all of this before, serving and attacking her way into the top ten as far back as 2016, and returning better in the last two years. If those two halves come together, we won’t see a (19) next to her name again for a long time.

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Can Clara Tauson Withstand the Winners?

*As long as she’s hitting this shot, Clara Tauson will be fine.*

Clara Tauson picked up her third career title in Auckland on Sunday. She claimed the trophy after losing the first set when her opponent, Naomi Osaka, retired with an abdominal injury. It isn’t the way she would have liked to have won it, and based on the first 45 minutes of play, she probably wouldn’t have beaten a healthy Osaka. But she earned her spot in the championship match, ousting top-seeded Madison Keys in the quarter-finals.

It was a long wait for the 22-year-old from Denmark. She won two titles and reached a third final in 2021, ultimately climbing to a peak rank of 33 in early 2022. Back and foot injuries derailed her progress, and she languished outside the top 50 for more than two years. Once one of the game’s leading prospects, she still has plenty left to prove.

Tauson’s signature is what tennis people call easy power. She whips through the ball, especially on the forehand, with such impeccable technique that her strokes shoot through the court faster than it looks like they ought to. The Kiwi crowd saw an excellent display of easy power on Sunday, as Osaka possesses the same magic to an even greater extent. Both players hit angled bullets that made their opponent look lazy. But there’s little point in chasing a well-placed groundstroke off the Tauson (or Osaka) racket.

The Dane is nearly as effective from the service line. Standing six feet tall with excellent control, she can break a returner’s spirit with one ball after another on the center line. On Sunday, she served three consecutive down-the-tee aces against Osaka. A fully fit opponent might have gotten a racket on one or two of them, but only a handful of women could have put them back in play. In the last 52 weeks, only Osaka, Qinwen Zheng, and Elena Rybakina have hit aces at a better clip.

The challenge for Tauson is, well, everything else. While her backhand sometimes looks strong, the results on that wing are middling. Her second serve does not befit a six-footer. Most problematic of all, she doesn’t defend well. She piles up plenty of winners, but the women across the net hit more.

Winners take it all

It’s tempting to say that Clara’s big-swinging game is in the high-risk, high-reward Kvitova/Ostapenko/Alexandrova mold. (Okay, no one could ever be like Jelena Ostapenko, but you know what I mean.) It’s easy to picture her smacking a forehand winner or sending a groundstroke wildly astray.

The numbers, however, don’t bear it out. My go-to metric for WTA game style is Aggression Score, which tells us how often–on a per-shot basis–a player ends the point for good or ill. Tauson comes in at +18, more aggressive than average, but barely. (Average is zero, with most players falling between -100 and +100.) That’s only marginally ahead of Jasmine Paolini (+10), in a different territory entirely from Osaka (+108) or Ostapenko (+251) over the last year.

We gain some insight by breaking that number down into its components. The 22-year-old scores often enough on her favorite wing, ending points with a winner (or forced error) with nearly one in five forehands she hits. Over the last 52 weeks, that’s good for 13th out of 75 women for whom we have sufficient data:

Player                    FH Wnr%  
Jelena Ostapenko            33.1%  
Naomi Osaka                 24.8%  
Lulu Sun                    22.2%  
Aryna Sabalenka             22.0%  
Ekaterina Alexandrova       21.6%  
Amanda Anisimova            20.8%  
Katie Boulter               20.5%  
Diana Shnaider              20.4%  
Danielle Collins            20.4%  
Anastasia Pavlyuchenkova    20.3%  
Donna Vekic                 20.1%  
Liudmila Samsonova          19.6%  
Clara Tauson                19.4%

She’s barely above average, however, by the backhand version of the same metric. Many of the women near the top of the forehand list take the same tactical approach off both sides. Ostapenko, Sabalenka, and Anisimova (among others) appear in the top ten by backhand winner rate, as well. Tauson, on the other hand, puts away backhands about as often as Bianca Andreescu or Jessica Pegula.

On the positive side, the Dane’s Aggression Score lags because she doesn’t hit a huge number of unforced errors. She takes more risks than the average WTAer on forehand–13% UFEs versus 11% for the tour as a whole–but fewer on the backhand–9% against 10%. Anisimova, by comparison, hits unforced errors on 14% of her forehands and 13% of her backhands.

Fewer errors is better, all else equal. But when Tauson works the point, her opponents tend to reap the rewards. She is much more successful in short points than long ones: Only a handful of players win fewer points in the 7- to 9-shot category. Prolonging the point has only so much value when you’re unlikely to win it. For someone with the 22-year-old’s skillset, better to swing away, accept more errors, and pick up that many more quick winners in exchange.

Flat-footed

The best illustration of what happens to Tauson in those (relatively) long points is the rate at which players hit winners against her. On average, about 29% of points end with a clean winner by either player, so the typical woman sees a winner fly by about 14.5% of the time. The Dane is near the top of the list:

Player              vs Wnr/Pt  
Angelique Kerber        22.5%  
Clara Tauson            21.0%  
Marie Bouzkova          20.9%  
Emma Raducanu           19.8%  
Elise Mertens           19.3%  
Caroline Wozniacki      18.8%  
Daria Kasatkina         18.6%  
Victoria Azarenka       18.2%  
Yulia Putintseva        18.2%  
Elina Avanesyan         18.0%

This isn’t bad company, exactly. But for a free-swinging forehand expert, it’s the wrong crowd. With the possible exception of Raducanu, these are players who cough up winners because they try to build points and sometimes fail. (Or in some of these cases, opponents feast on weak second–or even first–serves.)

The biggest hitters generally allow their opponents fewer winners than average, even if they aren’t the best movers or their defensive rally skills are subpar. Here are the tour’s top ten in winners per point over the last year. I’ve shown their winners against (vs Wnr/Pt) as well, and added Tauson to the list for comparison:

Player                 Wnr/Pt  vs Wnr/Pt  
Jelena Ostapenko        21.6%      11.5%  
Aryna Sabalenka         20.7%      12.0%  
Naomi Osaka             20.1%      14.8%  
Lulu Sun                20.1%      13.5%  
Elena Rybakina          19.1%      13.4%  
Ekaterina Alexandrova   19.1%      13.2%  
Ons Jabeur              18.9%      11.5%  
Danielle Collins        18.5%      13.1%  
Leylah Fernandez        18.2%      13.5%  
Donna Vekic             18.0%      15.5%  
…                                         
Clara Tauson            15.7%      21.0%

Of the top ten, only Osaka (barely) and Vekic allow more winners than average against them. None is even close to the previous list. One of the main benefits of an aggressive game style is that it takes the racket out of the other woman’s hand, even at the cost of some mishit service returns and wild groundstroke misses. Tauson, so far, has been unwilling to make that trade. It’s unclear whether she has the ability to post consistent wins with her more conservative approach.

Take the gamble

The Dane has some room to build on her current WTA rank of 41, but without unleashing more of her weapons, more of the time, I suspect she’ll get stuck on the wrong side of the top 20. Even if she can’t match the all-around barrage of someone like Sabalenka, she’d do better to follow that example than let herself turn into the next Elise Mertens.

In the 30 Tauson matches logged by the Match Charting Project, her Aggression Score in losses was +16. In victories, it was +36. (I grouped the Auckland final with the losses.) That’s not a slam-dunk case, especially since it lumps together matches from 2019 to today. But it hints that the 22-year-old plays better when she goes bigger.

One counter-example to that trend is instructive. Last week’s quarter-final against Keys was an unusually passive victory: Tauson won in straights despite an Aggression Score of -38. The American was more likely to seize the initiative, hitting exactly twice as many winners (and twice as many unforced errors) as the Dane. Tauson’s salvation was that Keys couldn’t do much against second serves. Keys won a dire 32% of second-serve return points–worse than she did against the Tauson first serve, and enough of a liability to swing the match in her opponent’s favor.

That kind of rescue is something that Clara rarely enjoys. Among the WTA top 50, she ranks 14th by first-serve win percentage. By second-serve win percentage, though, she’s fifth from the bottom. The percentage-point difference between her two numbers ranks with the biggest gaps on tour:

Player                  1st%   2nd%   Diff  
Qinwen Zheng           75.5%  46.8%  28.7%  
Coco Gauff             71.7%  43.8%  27.9%  
Ekaterina Alexandrova  69.5%  42.6%  26.9%  
Katie Boulter          70.8%  45.1%  25.7%  
Clara Tauson           69.2%  43.5%  25.7%  
Donna Vekic            70.7%  45.4%  25.3%  
Danielle Collins       70.5%  45.8%  24.7%  
Karolina Pliskova      67.4%  42.8%  24.6%  
Elena Rybakina         72.0%  48.6%  23.4%  
Naomi Osaka            74.5%  51.6%  22.9%

Qinwen is known for the disconnect between her two deliveries; Gauff spent much of the 2024 season struggling with double faults. More to the point, most of this group cleans up on first serve. Sure, Zheng or Rybakina would love to win more second-serve points, but their first-serve win rates are so high that it hardly holds them back.

Tauson’s first-serve success–even though it pales against that mostly-elite group–implies that she should be able to muster something better off the second delivery. She could take more chances: While her double-fault rate is above average, it is not worryingly high. More likely, she could use her height to push returners wide, then attempt to finish the job on the next shot. She shows us textbook examples of that play in almost every match, just not often enough.

The Dane has physical tools that will take her far in pro tennis. She’s doesn’t, however, have such extravagant gifts that she can get away with suboptimal tactics. Even in the tall-women’s club of the WTA, there aren’t many six-footers. It’s time that Tauson plays like one.

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Can Learner Tien Hang With the Big Boys?

*Learner Tien at the 2024 US Open. Credit: Hameltion*

Learner Tien has done little in 2024 except win. He reeled off a 28-match streak from May to late July, collecting five titles, including his first at the Challenger level. He reached the quarter-finals at the tour event in Winston-Salem. After picking up two more Challenger crowns and another final, the young American opened his NextGen Finals campaign yesterday with a victory over top-50 player Jakub Mensik, 21st on the Elo list.

If you don’t follow prospects, you can be forgiven if you’ve only recently learned the name. Tien is only two weeks removed from his 19th birthday. He opened the year only barely inside the top 500. There were plenty of reasons to expect big things from the young man–a national 18s title at 16, two junior slam finals–but it would have been foolish to predict so much, so soon.

One reason to moderate expectations is simply age. For those not named Alcaraz or Sinner, it takes time to develop into a top player. Only one man under the age of 21–the cutoff for this week’s event in Jeddah–is ranked inside the top 40. Before Tien turned 19 this month, he was the top-ranked 18-year-old in the world, even with a triple-digit number next to his name.

The climb to the top is even more challenging for youngsters who can’t rely on pure power. Mensik, the highest-ranked teenager, is six feet, four inches tall, with weapons that make him seem bigger. Novak Djokovic recently called him “one of the best servers we have in the game.” The Czech has plenty to learn, and he will surely continue to refine his game. But to compete at the top level, he doesn’t have to.

Tien doesn’t have that luxury. He stands five inches shorter than Mensik. While he may have a bit more growth coming, five-eleven is near the bottom edge of what can be managed on the ATP tour. Only 15 members of the top 100 stand less than six feet, and even that list is skewed toward clay-court specialists. Sebastian Baez is the only five-foot-anything ranked above 45th.

The playing styles available to shorter athletes are limited, especially on hard courts. Tien has already demonstrated his mastery of many of those tactics. He can use his left-handedness to swing serve after serve wide, to a righty’s backhand. He is sturdy from the baseline, and you can take that literally: He’s unafraid of claiming territory right up to the line itself, taking advantage of both his quickness and raw speed. Fearless counterpunching has paid dividends for smaller stars from Olivier Rochus to Kei Nishikori to Alex de Minaur. As a lefty, the American has options those men didn’t.

Still, Tien’s transition from the Challenger tour to the big leagues could be rocky. Good defense and well-executed tactics are enough to clean up against top-200 competition. The combination was (just barely) sufficient against Mensik yesterday. But a full-time spot on the ATP tour requires more.

The game plan

For such a middling server, Tien wins a remarkable number of serve points. He ranks among the top quarter of Challenger tour regulars by serve points won, though his number is helped a bit by spending the entire year on hard courts. He does even better–64.6% compared to a tour norm below 62%–when aces and double faults are taken out of the equation. When the returner gets a racket on the ball, only ten players were better on hard courts.

It’s not surprising, then, that Tien excels on return. Among Challenger players with at least ten matches at the level in 2024, only two men–Dalibor Svrcina and his fellow American in Jeddah, Nishesh Basavareddy–topped Learner’s 42.5% clip. Tien is particularly effective converting second-serve return points.

He’s even better–or at least, he has been better this season–with more on the line. His rate of return points won rises to nearly 47% on break point chances, and he’s just as clutch on the other side of the ball. He saved 65.6% of the break points he faced, second at Challenger level to Mikhail Kukushkin. Here, he has already learned how to use the lefty serve, alternately forcing opponents far out wide and sticking them with uncomfortable body serves when he catches them leaning left for the slider.

The overall package is something between those of two other left-handers, Adrian Mannarino and Cam Norrie. Mannarino, also a sub-six-footer, throws the kitchen sink at opponents, keeping them off balance to compensate for his own lack of power. Norrie is considerably taller and has more firepower at his disposal. But he, too, refuses any rhythm to the man across the net. He alternates a loopy forehand with a flat backhand–except when he doesn’t, if you ever think you’ve found a groove.

Tien serves like Mannarino out of necessity. Even if he doesn’t get taller, the American will surely get stronger, so his 90-mile-per-hour first serves from this year’s US Open probably won’t tell the story of his entire career. But at the moment, he relies on angles and variety. Mannarino has overcome his limitations to the tune of a top-20 peak ranking. On the other hand, his playing style (and the comically loose string tension it relies on) is so unique he hardly provides an example to follow.

In the Las Vegas Challenger final back in September, Tien looked particularly like Norrie. Fighting the wind, he spun forehands and zinged backhands, a combination that made it impossible for the bigger-hitting Tristan Boyer to get comfortable. In other settings, though, the youngster is increasingly using his forehand as a (flatter) weapon, building points one sharp angle at a time.

The most instructive element of these comparisons, though, is the way in which the American differs from his fellow lefties. Mannarino reached Tien’s current ranking when he was 21, after more than 250 pro matches. Norrie–who ultimately peaked inside the top ten–played three years of college tennis and didn’t approach the top 100 in the world until he was 22. Tien, by contrast, is clearing all these hurdles on the first try. Deploying a brainy playing style that normally takes years to refine, the American is making it look natural.

The projection

Aside from size and serve speed, Tien’s future looks bright. The 19-year-old has won 61 of 73 matches across all levels this year. Within a few months, he is likely to crack the top 100. At Challenger level, his serve hasn’t held him back: As we’ve seen, he wins more service points than most of his peers, despite gaining fewer free points with the serve itself.

The question, then, is what effect Tien’s attributes have on career trajectory. Everyone wins fewer points at tour level than at Challengers–the competition is better, so it would be weird if it were otherwise. But the ratio isn’t uniform. Mannarino has won about 7% fewer serve points at tour level than he did in hard-court Challenger matches, while Marcos Giron (another sub-six-footer) lost less than 1% in the transition.

These Challenger-to-tour conversions offer some insight into Learner’s future. Since he has played almost all of his pro matches on hard courts, we’re going to calculate something a bit quirky. How do serve and return win rates change from hard-court Challenger matches to all tour-level matches? That’s what we want to know for the 19-year-old: He’ll need to play on all surfaces soon, probably starting in 2025. This transition he’s about to make–how did it go for other players?

The first-pass answer is that pros are able to retain something like their hard-court Challenger serve win percentage, seeing that number drop by 2%. But they lose a lot against tougher competition on return, winning 7.1% fewer return points. The following table shows those numbers (“Conv%”), along with Tien’s career record at hard-court Challengers (“Tien CH”), along with what the conversion factors suggest for his tour-level win rates (“Tien Adj”):

        Conv%  Tien CH  Tien Adj  
Serve   98.0%    63.3%     62.0%  
Return  92.9%    42.3%     39.3%

Those are awfully respectable numbers. 62% serve points is marginal for a tour regular, but combined with 39.3% return points, it’s enough. The combination is about what Francisco Cerundolo managed this year, and he’s ranked 30th in the world.

A word of caution: This type of conversion is not suggesting that Tien’s level is the same as Cerundolo’s now. The calculation involves taking each active player’s career records in tour and Challenger main-draw matches. That probably underestimates Tien’s potential, because most men play the majority of their Challenger matches after their 19th birthday. But a player’s career numbers will include their peak, which typically comes much later. At the very least, these numbers suggest Tien could reach Cerundolo’s level (or better) eventually.

The (other) adjustments

That’s just a first-pass number, because we haven’t gotten to height and handedness. Taking those into account does not help Learner’s case.

Lefties, it turns out, have a rougher transition than right-handers do. Here are the serve and return conversion factors, separated by hand:

        Lefties  Righties  
Serve     97.3%     98.1%  
Return    92.1%     93.0%

Not a huge difference, but hey, the margins in tennis are small. I suspect it is slightly harder for left-handers to move up a level for two reasons. First, the less experienced the opponent, the more valuable it is to be unusual, and lefties are certainly that, making up barely one-tenth of the player pool. At tour level, the novelty is gone: ATP regulars generally know how to handle left-handers.

Second, lefties are more likely to get by with what we might call “crafty” tennis, rather than power. (That’s related to the first reason: They’ve reached Challenger level because they’ve outsmarted inexperienced opponents thus far.) Craftiness might be enough against #180 in the world, but against, say, the Hurkacz serve, all craftiness gets you is a few more tuts of approval in the press box.

Whatever the reason, Tien’s left-handedness means we need to update our tour-level forecast:

    (L) Conv%  Tien CH  Tien Adj  
Serve   97.3%    63.3%     61.6%  
Return  92.1%    42.3%     39.0%

Not a huge hit, but ~0.4% of total points won is roughly equivalent to four places in the rankings. A small number here ultimately translates to much bigger ones when denominated by tour-level prize money.

And then, size. Here are the conversion factors for players in three height categories: under six feet, from six feet to six-foot-three, and above six-foot-three:

        under 6'0  6'0 to 6'3  over 6'3  
Serve       97.0%       97.9%     99.0%  
Return      92.0%       93.4%     92.6%

Again, craftiness doesn’t convert. Players under six feet tall lose the most points between hard-court Challengers and tour level. The tallest players remain almost as effective on serve, while the middle category retains the most of their return effectiveness.

Here’s the Tien update, using the sub-six-feet conversion rates:

        (< 6') Conv%  Tien CH  Tien Adj  
Serve          97.0%    63.3%     61.4%  
Return         92.0%    42.3%     38.9%

Not much of a difference from the left-handed numbers, though we keep going down. This is increasingly the profile of a clay-court specialist, and we might be outside the top 40 now.

Of course, Learner is both left-handed and (relatively) small. My mini-study of active players doesn't give us a big enough pool of data to extrapolate from the small group of small lefties. Instead, a back-of-the-envelope combination of the two factors gives us conversion factors of 96.3% for serve and 91.3% for return:

        (L&Sm) Conv%  Tien CH  Tien Adj  
Serve          96.3%    63.3%     61.0%  
Return         91.3%    42.3%     38.6%

For the first time, the adjusted versions of Tien's Challenger-level stats are underwater, summing to less than 100%. Winning 61% of service points would rate fourth-worst in the current ATP top 50, just ahead of Sebastian Baez. 38.6% on return is respectable, though not enough to consistently challenge for titles when combined with such a mediocre serve.

The exact numbers are not important: For one thing, we don't have enough recent data to know exactly how size and handedness interact. Maybe it's not quite that bad. Suffice it to say that both lefties and undersized players are more likely to struggle in the transition from Challengers to the full tour. A player who fits both categories should not expect a smooth trip up the ladder.

For Tien to beat these projections, all he has to do is improve more than the average pro does. As noted above, he already has something of an edge: He posted most of his excellent Challenger numbers as an 18-year-old. That's Alcaraz territory. At the same age, Mannarino was struggling at Futures level, and future top-tenner Norrie was headed off to college. If for some reason Tien plays a lot of Challenger matches in 2025, his stats will probably look better, and the tour-level predictions would change as well.

As Learner and his team are undoubtedly aware, those improvements need to center on the serve. The youngster probably already has what it takes to break serve once or twice a set on tour. But without a bigger first-strike weapon, he'll struggle to get those opportunities. Yesterday he withstood Jakub Mensik's event-record 24 aces, winning in a fifth-set tiebreak despite losing 14 more total points than Mensik did. The American played brilliant tennis, yet it took luck and brilliant timing to pull out the victory. For a five-foot-eleven left-hander among the giants of the professional game, it's not the last tightrope he'll have to walk.

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Mirra Andreeva’s Many Happy Returns

*Mirra Andreeva at the 2024 Paris Olympics.*
*Credit: Like tears in rain*

Mirra Andreeva is the best teenager on the WTA tour, and it isn’t close. She’ll finish 2024 ranked 16th on the official points table, more than one hundred places ahead of her closest teenage competitor, Maya Joint. Andreeva is a year younger than Joint, and she’s two years younger than Ella Seidel, third on the under-20 list.

Players who outpace their fellow teenagers typically go on to notable careers. Here’s the list of top teenagers at the end of each season this century:

Year  Player                    Rank  
2000  Serena Williams              6  
2001  Kim Clijsters                5  
2002  Kim Clijsters                4  
2003  Vera Zvonareva              13  
2004  Maria Sharapova              4  
2005  Maria Sharapova              4  
2006  Maria Sharapova              2  
2007  Nicole Vaidisova            12  
2008  Agnieszka Radwanska         10  
2009  Caroline Wozniacki           4  
2010  Anastasia Pavlyuchenkova    21  
2011  Christina McHale            43  
2012  Sloane Stephens             38  
2013  Eugenie Bouchard            32  
2014  Madison Keys                30  
2015  Belinda Bencic              14  
2016  Daria Kasatkina             26  
2017  Catherine Bellis            46  
2018  Dayana Yastremska           58  
2019  Bianca Andreescu             5  
2020  Iga Swiatek                 17  
2021  Emma Raducanu               19  
2022  Coco Gauff                   7  
2023  Coco Gauff                   3  
2024  Mirra Andreeva              16

There’s no such thing as a can’t-miss prospect in women’s tennis, but showing up on this list gets you pretty close. Andreeva’s case is particularly extreme, because she is still just 17 years old.

In the under-18 category, the young Russian has virtually no competition. Only three other under-18s rank among the top 200, none closer than Alina Korneeva at 176th. No woman so young has finished inside the top 20 in almost two decades, going back to Nicole Vaidisova’s top-ten showing in 2006.

Here’s another way to look at what Andreeva has accomplished. With four victories to reach the Ningbo final in October, she increased her career tour-level main-draw win count to 48. Take a look at the list of all women, post-Vaidisova, to post even 30 such wins before their 18th birthday:

Wins  Player              Last Win as 17yo  
32    Victoria Azarenka         2007-07-30  
47    Caroline Wozniacki        2008-06-23  
42    Tamira Paszek             2008-09-15  
32    Donna Vekic               2014-06-23  
33    Amanda Anisimova          2019-07-29  
64    Coco Gauff                2022-03-07  
48    Mirra Andreeva            2024-10-14

Again, good company, and think of all the stars who aren’t here. You know, everybody (besides Vekic) for a decade. In this entire time span of about 17 years, Andreeva has done more at her age than anyone except Coco Gauff. The Russian might even erase that caveat. She doesn’t turn 18 until the end of April, and this year, she had won 12 matches by that time. 17 wins–enough to surpass Gauff–is hardly out of reach.

Let’s turn now to how Andreeva is achieving so much success, and why she might soon lop a digit off of her age-defying ranking.

Returns first

Forget about all this under-18 and teenager stuff for a minute. Mirra is already one of the best returners in the game. Here are the top dozen WTA tour regulars, ranked by return points won:

This isn’t a perfect measure. For one thing, Andreeva faced one of the weaker schedules of players on this list. Her median opponent was ranked 58th, compared to 30th for Iga and 42nd for Coco. It would take considerably more work to suss out whether Andreeva’s 47.3% of return points won, against her set of opponents, is better or worse than, say, Aryna Sabalenka’s 45.3% against competition nearly as stiff as Swiatek’s.

The quibbles mean that we can’t quite proclaim the Russian a top-three returner. The point, though, is that she’s in the conversation. In fact, if we narrow our view to matches against top-20 players–limiting if not eliminating the influence of each woman’s schedule–Andreeva hangs on to her position:

(We’re not talking about Iga today, but… 47% of return points won against top-20 opponents? My word.)

Where Andreeva shines even brighter is against first serves. She won first-serve return points at a higher clip than any other woman on tour this year:

Player               1st RPW%  
Mirra Andreeva          42.6%  
Coco Gauff              42.1%  
Marketa Vondrousova     40.8%  
Iga Swiatek             40.8%  
Daria Kasatkina         40.7%  
Marta Kostyuk           40.5%  
Elina Avanesyan         40.0%  
Jasmine Paolini         40.0%  
Katerina Siniakova      39.5%  
Karolina Muchova        39.5%

Put that in perspective: Andreeva wins more first-serve return points than Barbora Krejcikova (to pick one name from several) wins all return points.

Again, the Russian’s stats are influenced by her level of competition. Against top-20 opponents, Mirra falls to third place, behind Swiatek and just back of Gauff. But you get the idea. To say, “Well, actually, she’s not quite up to Gauff’s standard” is to say we’re dealing with a special player.

Precocious patience

Andreeva’s serve is good for a 17-year-old, but as we’ve seen, it’s not the side of her game that has put her in the top 20. Her returns, and by extension, her baseline play, are responsible for that.

Among top players, Mirra is currently most similar to countrywoman Daria Kasatkina. The two Russians, according to Match Charting Project data, post average rally lengths of 4.9 strokes, more than anyone else in the top 40. Both women are effective off both wings; Andreeva’s backhand is the better of the two, while Kasatkina’s forehand scores more points. The teenager is a bit more likely to force the issue: While both rank well below average in Rally Aggression Score, Mirra is closer to the norm.

A key difference shows up in their rally breakdowns. Again based on the subset of matches logged by the Match Charting Project, here are each woman’s percent of points won at various rally length categories:

Player     1-3 W%  4-6 W%  7-9 W%  10+ W%  
Andreeva    49.8%   48.6%   51.8%   53.8%  
Kasatkina   48.0%   45.6%   51.0%   52.5%

The first thing that pops out here is that Andreeva is better in every category, something that reflects both the vagaries of the uneven tennis schedule and the non-random nature of Match Charting Project samples. However you slice it, Mirra won more points, though my Elo rankings agree with the official formula that Kasatkina was the better player.

To get a better idea of what we’re looking at, let’s normalize each woman’s rally-category splits as if they won exactly half of their overall points:

Player     1-3 W%  4-6 W%  7-9 W%  10+ W%  
Andreeva    49.5%   48.3%   51.5%   53.5%  
Kasatkina   49.6%   47.1%   52.7%   54.2%

The teenager holds the edge in the 4-6-stroke category, while Kasatkina looks better in the longer rallies.

That 4-6-shot category tells us more than it lets on. Andreeva’s 48.3% (or the un-normalized 48.6%) doesn’t look very impressive. Points in this group account for one quarter of all the points she plays, and she loses more than half.

But consider her playing style. Medium-short rallies are often determined by the lingering influence of the serve: The returner might withstand a plus-one attack, only to leave a sitter for the server to put away. Or a strong return doesn’t finish the point, but the returner’s next shot–the fourth stroke of the rally–does the job. 4-6-shot rallies go disproportionately to big hitters: Aryna Sabalenka led the category this year.

For someone like Andreeva or Kasatkina, the task is to limit the damage. Get the serve back, try to neutralize the point. Place serves where aggressive returners won’t do too much damage. If a big return comes back, play the same defense that works against the serve. Kasatkina has all of those skills, but there is only so much she can do. Mirra, with her flatter strokes and somewhat bigger weapons, can keep opponents from running away with these medium-short points. She’ll lose sometimes to the likes of Sabalenka, but unless they catch her on an off day, she won’t be blown off the court.

Growth potential

If Andreeva could be characterized as a younger, somewhat more aggressive Kasatkina, that would be a pretty good compliment for a 17-year-old. But the teenager promises to become much more.

One of my favorite bits of counterintuitive tennis wisdom is that return stats rarely improve. Returning is based on a set of skills–anticipation, quickness, speed–that, on net, decline with age. Whatever tactical savvy a player picks up as she ages will, at best, cancel out the age-related decline. This isn’t an iron law, but it’s surprising how often players reach their peak return effectiveness very early in their careers.

The same is not true for the serve. 17-year-olds (or, hey, 23-year-olds) have the capacity to get stronger. Footspeed and reaction time don’t figure into the serve, so with better coaching or targeted practice (think late-career Djokovic), serve stats can improve even as the rest of a player’s game declines. A couple of examples: Maria Sakkari steadily improved her first-serve win rate from the 13th percentile to the 93rd percentile in five years. Simona Halep’s first-serve was in the top quarter of tour regulars in 2014; two years earlier, it had been one of the WTA’s worst.

The implications for Andreeva are clear. We don’t need to wishcast an improvement in her return game: She’s already one of the best returners in the game. Instead, the road to the top ten and beyond goes through her serve. Her results so far are adequate. She won 58.4% of her serve points in 2024, compared to a top-50 average of 58.7%. When we consider how much she played on clay, that number looks a bit better. On hard courts, she won more serve points than average.

Mirra, then, doesn’t face the same uphill struggle that Sakkari and Halep overcame. Her potential trajectory is more like, say, Victoria Azarenka’s. Vika arrived on the scene as a killer returner with a good-enough serve. In 2009 and 2010, she won nearly half of her return points against 58% to 59% of her service points. That combination earned her two top-ten finishes. (She was a few years older than Andreeva at that point, yet another reminder of how unique the Russian’s early success has been.)

Two years later, Azarenka boosted her rate of serve points won to 61%. Combined with the same results on return that had gotten her into the top ten, the bigger serve earned her six titles–including her first major–and the year-end number one ranking. 59% to 61% may not sound like much, but for an elite returner, that’s all it takes.

If Andreeva did the same, lifting her 58.4% serve-point win rate to 61%, she’d be the ninth-best server on tour. Remember how she’s just a tick behind Coco Gauff on return? A Vika-like serve boost would put her ahead of the American in that category, outweighing Coco’s narrow edge on return. Shorter version: She’d be a top-three player, maybe more.

None of this is guaranteed. It may not–it probably won’t!–happen right away. For every Azarenka, there’s a Nicole Vaidisova or, worse, an injury victim like Catherine Bellis. Still, few paths to the top are marked so clearly. For Mirra Andreeva, a modest, achievable set of improvements are all that stand between her and the top.

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How Does Jannik Sinner’s Season Stack Up?

Jannik Sinner just wrapped up a season for the ages. He won both hard-court majors, three Masters 1000s, and the Tour Finals. He led Team Italy to a Davis Cup championship and ended his campaign on a 26-set winning streak.

By November, the Italian was no longer competing against the field: He was gunning for a place in the record books. He went undefeated against players outside the top 20. Not a single player straight-setted him: He won at least one set in each of his 79 matches. Only Roger Federer, in 2005, had ever managed that.

After Sinner won the Australian Open, I wrote that Yes, Jannik Sinner Really Is This Good. Since then, he got even better. In the seven-month span ending in Melbourne, the Italian held 91.1% of his service games, a mark that not only led the tour but put him in the company of some of the greatest servers of all time. For the entire 2024 season, he upped that figure to 91.5%–including thirteen matches on clay.

He also defied the most powerful force in all of sport, regression to the mean. Sinner’s hold percentage was aided by some sterling work saving break points. He won tons of service points, of course, but he was even better facing break point. The average top-50 player is worse: Good returners generate more break points, so it’s a tough trend to defy.

In the 52 weeks ending in Melbourne, Sinner had won three percentage points more break points than overall service points. I wrote then: “I can tell you what usually happens after a season of break-point overperformance: It doesn’t last.” In the Italian’s case, though, it did. In 2024 as a whole, he won 71.1% of service points, and 73.6% of break points. He would have enjoyed a productive season without repeating his break-point overperformance, but those two-and-a-half percentage points explain much of the gap between very good and historically great.

Clubbable

Most players who serve so effectively are middling returners. The Italian has bucked that trend as well.

Late in 2023 I wrote about tennis most exclusive clubs–Alex Gruskin’s method for identifying standout players by their rankings in the hold and break percentage categories. It’s rare for anyone to crack the top ten in both. In 2023, Sinner signaled what was coming by finishing in both top fives. He ranked fifth by hold percentage and fourth by break percentage. Most seasons, that would have been enough for a year-end number one, but Novak Djokovic was even better, finishing in the top three on both sides of the ball.

Sinner, as we’ve seen, served even better this year. His 91.5% hold percentage was well clear of the pack, even with the resurgence of countryman Matteo Berrettini and increased time on tour from rocket men Ben Shelton and Giovanni Mpetshi Perricard. Last season, Djokovic led the tour by holding 88.9% of his service games. That’s impressive, especially for a guy known for other parts of his game, but it wouldn’t have cracked the 2024 top three. The Italian set a new standard.

At the same time, his return barely flagged. He fell out of the the top five by the narrowest of margins, winning nearly as many return games as he did in 2023 but falling to sixth place. Still, a “top-six club” showing is plenty rare. The only players who have posted one since 1991 (when these stats became available) are Djokovic, Nadal, Federer, and Andre Agassi. Federer only managed it once. Sinner has now done it twice.

The Italian’s return skills are even more impressive when we compare him the other season-best servers of the last thirty-plus years. The following table shows the hold-percentage leader for each year, along with his break percentage and his rank (among the ATP top 50) in that category:

Year  Player             Hold%   Brk%  Rank  
1991  Pete Sampras       87.3%  25.4%    40  
1992  Goran Ivanisevic   88.8%  20.4%    48  
1993  Pete Sampras       89.6%  27.7%    19  
1994  Pete Sampras       88.4%  29.3%    19  
1995  Pete Sampras       89.0%  26.0%    25  
1996  Pete Sampras       90.8%  20.8%    43  
1997  Greg Rusedski      91.6%  16.7%    50  
1998  Richard Krajicek   89.2%  21.4%    41  
1999  Pete Sampras       89.7%  21.7%    44  
2000  Pete Sampras       91.7%  18.4%    49  
2001  Andy Roddick       90.4%  19.7%    45  
2002  Greg Rusedski      88.5%  17.6%    48

Year  Player             Hold%   Brk%  Rank    
2003  Andy Roddick       91.5%  20.9%    43  
2004  Joachim Johansson  91.9%  14.5%    48  
2005  Andy Roddick       92.5%  20.8%    45  
2006  Andy Roddick       90.5%  22.4%    43  
2007  Ivo Karlovic       94.5%   9.8%    50  
2008  Andy Roddick       91.2%  19.2%    40  
2009  Ivo Karlovic       92.2%  10.3%    50  
2010  Andy Roddick       91.1%  17.6%    47  
2011  John Isner         90.7%  12.9%    50  
2012  Milos Raonic       92.7%  15.1%    49  
2013  Milos Raonic       91.4%  15.7%    49  
2014  John Isner         93.1%   9.3%    49  

Year  Player             Hold%   Brk%  Rank  
2015  Ivo Karlovic       95.5%   9.6%    50  
2016  John Isner         93.4%  10.9%    49  
2017  John Isner         92.9%   9.6%    50  
2018  John Isner         93.8%   9.4%    50  
2019  John Isner         94.1%   9.7%    49  
2020  Milos Raonic       93.9%  18.0%    44  
2021  John Isner         91.1%   8.8%    50  
2022  Nick Kyrgios       92.9%  19.3%    40  
2023  Novak Djokovic     88.9%  28.8%     3  
2024  Jannik Sinner      91.5%  28.3%     6

If it hadn’t been for Djokovic’s appearance at the top of last year’s list, Sinner’s 2024 campaign would be hardly recognizable. Even Pete Sampras struggled to hold on to a spot in the break-percentage top 20. Circuit-best servers simply aren’t supposed to win so many return games, yet Sinner threatens to make it the new normal.

Carrot yElo

The Italian’s 73 wins, including 18 against the top ten, took his Elo rating to new heights. He began the year with a career-high rating of 2,197, second on the circuit to Djokovic. He quickly took over the top spot, ultimately clearing the 2,300 mark with his victory at the Tour Finals.

Elo is not a perfect measure to compare players from different eras, but in my opinion, it’s the best we’ve got. It’s the basis of my Tennis 128, which Sinner will join as soon as I get around to updating the calculations. 2,300 is rarefied air: In the last half-century, he is only the twelfth player to reach that mark. With three singles victories to secure the Davis Cup, he nudged his rating up to 2,309, surpassing Mats Wilander and establishing the eleventh-highest peak since the formation of the ATP.

A stratospheric Elo is an indication of an outstanding player at the top of his game, but the metric is not designed to rate seasons. The alternative is yElo, a variation I devised for exactly this purpose. yElo works the same way as Elo does, adding or subtracting points based on wins, losses, and the quality of opposition. But unlike the more traditional measure, each player starts the season with a clean slate.

By regular Elo, Sinner holds a 150-point lead over second-place Carlos Alcaraz. By yElo, with its narrower focus, the Italian is even more dominant:

(The won-loss records are a bit different from official figures because my Elo and yElo calculations exclude matches that ended in retirement.)

The two-hundred-point gap between Sinner and Djokovic is one of the largest ever. Again going back to 1973, it ranks fourth. Only 2004 and 2006 Federer (over Lleyton Hewitt and Nadal, respectively) and 1984 John McEnroe (over Wilander) outpaced the competition by such a substantial margin.

By raw yElo, Sinner’s 2024 isn’t quite so historic. It’s the 26th best of the last half-century: An impressive feat, but not as close to the top of the list as some of the other trivia suggests. Here’s the list:

Year  Player              W-L  yElo  
1979  Bjorn Borg         84-5  2499  
1984  John McEnroe       82-3  2476  
2015  Novak Djokovic     82-6  2458  
1985  Ivan Lendl         82-7  2440  
2016  Andy Murray        78-9  2416  
2013  Novak Djokovic     74-9  2408  
1976  Jimmy Connors      97-7  2406  
1977  Bjorn Borg         78-6  2403  
1977  Guillermo Vilas  133-13  2401  
2006  Roger Federer      91-5  2399  
1980  Bjorn Borg         70-5  2395  
1981  Ivan Lendl        96-12  2383  
1987  Ivan Lendl         73-7  2381  
1982  Ivan Lendl        105-9  2380  
1978  Jimmy Connors      66-5  2379  

Year  Player              W-L  yElo  
2013  Rafael Nadal       74-7  2373  
1986  Ivan Lendl         74-6  2369  
2011  Novak Djokovic     63-4  2367  
2005  Roger Federer      80-4  2364  
2014  Novak Djokovic     61-8  2363  
2012  Novak Djokovic    73-12  2360  
1978  Bjorn Borg         79-6  2359  
2008  Rafael Nadal      81-10  2352  
1986  Boris Becker      69-13  2347  
1982  John McEnroe       71-9  2341  
2024  Jannik Sinner      72-6  2339  
1983  Mats Wilander     80-11  2338  
1974  Jimmy Connors      94-5  2332  
1989  Boris Becker       64-8  2329  
2015  Roger Federer     62-11  2329

One factor holding back Jannik’s 2024 is the number of matches played. Elo, in part, reflects the confidence we have in a rating. Winning 90% of 100 matches (or almost 150, in the case of Vilas) gives us more confidence in an assessment than 90% of 80 matches.

Another issue is that Elo has opinions about strong and weak eras. Going 70-5 in 1980 doesn’t look much different than 72-6 today, but Elo considers Bjorn Borg’s peers to have been stronger than Sinner’s. If Sinner and Alcaraz continue to improve and a couple of their peers emerge as superstars in their own right, then a 72-6 season might rank much higher.

The asphalt jungle

A couple of months ago, pundits started mulling where Sinner’s 2024 stood among the greatest hard-court seasons of all time. Since then, he piled on so many more wins that the qualifier wasn’t needed. Yet it remains a valid question.

The Italian’s highlights came almost entirely on hard courts. He won 53 of 56 matches, 42 of them in straight sets. He’s plenty skilled on natural surfaces, but given a predictable bounce and conditions that emphasize his power and penetration, opponents don’t stand a chance.

I don’t publish surface-specific yElo ratings, because they have limited usefulness for much of the year. For our purposes, though, hard-court yElo–same algorithm, limited to matches on one surface–is just the ticket. By this measure, Sinner’s 2024 is the eighth-best of all time:

Year  Player          Hard W-L  Hard yElo  
2015  Novak Djokovic      59-5       2426  
2013  Novak Djokovic      53-5       2413  
2012  Novak Djokovic      48-5       2377  
2005  Roger Federer       49-1       2374  
2006  Roger Federer       59-2       2373  
1995  Andre Agassi        52-3       2370  
2016  Andy Murray         48-6       2363  
2024  Jannik Sinner       52-3       2353  
2010  Roger Federer       45-7       2338  
2014  Novak Djokovic      40-6       2334 

Year  Player          Hard W-L  Hard yElo   
2014  Roger Federer       56-7       2333  
1985  Ivan Lendl          29-3       2332  
1987  Ivan Lendl          33-2       2325  
1996  Pete Sampras        46-4       2319  
2015  Roger Federer       38-6       2318  
1981  Ivan Lendl          41-3       2317  
2011  Roger Federer       45-7       2314  
2009  Novak Djokovic     53-10       2309  
1985  John McEnroe        25-1       2309  
1986  Ivan Lendl          30-2       2298

So, um, peak Djokovic was pretty good, huh?

Even though Elo doesn’t hold the rest of the 2024 field in particularly high regard, Sinner’s season was so dominant that he does well by this measure. A year that would rate as Djokovic’s fourth-best, Federer’s third, or Agassi’s second, is truly something worth celebrating.

The Italian still has some ground to cover before he challenges Novak, Roger, and the rest for all-time hard-court dominance. But he has already upped the standard for the 2020s and posted one of the most remarkable two-year spans in the game’s history. Sinner has built an enormous gap between himself and the field, and it is increasingly difficult to see how his peers will close it.

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Jasmine Paolini’s High-Wire Act

*Jasmine Paolini at the 2022 Transylvania Open. Credit: Nuta Lucian*

There are unorthodox aging curves, and then there’s whatever the hell Jasmine Paolini is doing right now. The best women tennis players tend to make their presence known in their late teens. I wrote earlier this year about the “improbable rise” of 22-year-old Emma Navarro.

Paolini is 28.

When Paolini was the age that Coco Gauff is now, she was ranked just inside the top 300, fresh off a first-round loss at an ITF $25K in Bulgaria. When she was the age that Iga Swiatek is now, she had finally cracked the top 150, about to head to Wimbledon qualifying. (She lost in the first round there, too.) When she was the age that Aryna Sabalenka is now, she had just stumbled through a four-match losing streak to the likes of Jil Teichmann and Irina-Camelia Begu that knocked her out of the top 50.

Just 16 months ago, Paolini was once again outside the top 50. For a five-foot, four-inch counterpuncher with no obvious weapons, she had achieved a great deal. There was little reason, though, to think she could climb much higher. Her peers were getting bigger, the game was becoming ever more aggressive, and she was reaching the age at which WTA stars begin to think about what else life might hold for them.

Then she started winning.

Since leaving Wimbledon last year, the Italian has won 66 of 99 matches, including two major semi-finals and five top-ten scalps. She picked up her first 1000-level title and made four other finals. Yesterday, she led Team Italy to a Billie Jean King Cup crown, starring in both singles and doubles en route to the championship. Her ranking is up to an astonishing 4th in the world. As if that weren’t enough, she’s in the top ten in doubles.

None of this was supposed to happen. Paolini’s late-2023 surge to the top 30 was one thing; what has happened since simply defies belief. How has she managed it? Is it a fluke, or will we see the Italian at the 2025 year-end championships as well?

Opportunistic effects

First, a bit of a caveat. Paolini, like Taylor Fritz, has played the official ranking system like a Stradivarius. She reached only three finals in 2024, yet two of them were slams. The other was a 1000. She earned huge chunks of points for a semi-final defeat of Mirra Andreeva at Roland Garros, a semi-final squeaker against Donna Vekic at Wimbledon, and a Dubai title that didn’t require her to face a top-ten opponent.

None of this is meant to take away from Paolini’s accomplishment. She beat the players in front of her, and in the case of Andreeva, she did so in emphatic fashion. The point is that her top-four finish has more to do with good timing than consistently dominant play.

My Elo ratings offer a second opinion, using an algorithm based on the quality of her opponents, rather than the venue and round of each match. By Elo, she stands in 9th place, just ahead of Madison Keys and Diana Shnaider, well back of Jessica Pegula and Elena Rybakina. Still a very good season, if a bit less astounding.

Even more revisionist is the total-points-won leaderboard. Going into the BJK Cup Finals, Paolini had won 51.8% of her total points this season. That’s a respectable rate, especially for someone who hovered in the 50% range for most of her tour-level career. But it is not typically top-five, or even top-ten material:

By this metric, the Italian stands in 19th place among the WTA top 50, behind a handful of players who didn’t even crack the official top 20. That doesn’t really mean she’s the 19th best player on tour: She faced one of the toughest schedules of anyone. Much as I love both Yulia Putintseva and counterintuitive arguments, I’m not going to try to convince you that Putintseva had the better season.

Still, Paolini’s position on the TPW list tells us something about how she won her matches. She didn’t lose many blowouts, but she didn’t win many, either. (She certainly didn’t get in the habit of spanking opponents like Swiatek and Sabalenka do.) Ten of her wins required a third set. Two victories–including the Wimbledon semi-final–came despite losing more points than she won.

The margins were not so narrow that we can ascribe the Italian’s breakout to luck. (Though the Vekic match could have gone either way, to say the least.) But this is the high-wire act that took Paolini to the top. She doesn’t have the tools to bludgeon her opponents. She has done a lot of things right to win 42 matches this year. To keep winning at a two-of-three clip, she’ll need to continue executing the new game plan to near-perfection.

The new game plan

It’s a bit tricky to isolate the key changes in Paolini’s approach, because–like Qinwen Zheng–she’s doing almost everything better than she did before the surge. That said, a few things stand out.

Check out the Italian’s breakdown of points won by rally length (in Match Charting Project-logged matches) before this season, compared with her performance this year:

Span     1-3 W%  4-6 W%  7-9 W%  10+ W%  
2016-23   49.1%   46.5%   51.0%   49.4%  
2024      49.8%   54.3%   56.6%   49.1%

Paolini’s improvement in 7- to 9-stroke rallies is significant, and her gain in the 4- to 6-shot category is enormous. In very short points and very long ones, little has changed.

Especially in the categories of shorter points, we need to keep in mind what these win rates measure. It’s tempting to think of a prototypical short point, then imagine Paolini, instead of her opponent, winning it. But the length of a given point is not handed down to us by God. When someone like Paolini starts winning more shorter points, it’s because she is ending them before they become long points, and/or she is preventing her opponents from ending points quickly.

The Italian can hardly stack up one-shot points (unreturned serves), and she can’t even reliably put away plus-ones–though she is doing that more than she used to. Instead, like the expert doubles player she has become, she can structure points that inch closer and closer to a point-ending opportunity. Call it plus-two tennis, aggressive point construction for undersized counterpunchers.

The plus-two forehand

Tactics are one thing; Paolini is a top-ten player because she has executed them so well. Her forehand is a big reason why.

She is ending points with her forehand at a much better clip than she did before the calendar flipped to 2024, and her inside-out forehand has seen particular improvement:

Span     FH Wnr%  DTL Wnr%  IO Wnr%  FHP/100  
2016-23    11.7%     17.7%     6.2%      2.9  
2024       17.5%     25.2%    13.3%     10.2

Here, “winners” refer to both clean winners and shots that induce forced errors. Through 2023, Paolini’s forehand winner/forced error rate of less than 12% put her in the bottom quarter of tour regulars. 17.5% moves her to the top third, not far behind Swiatek and Keys. The same stat for inside-out forehands (IO Wnr%) doesn’t put her in quite the same company, but it is an even better reflection of the tactical shift. Before, the Italian rarely used that shot as an offensive weapon; now it is a regular part of the arsenal.

The bottom line is reflected in the Forehand Potency (FHP/100) numbers. The number of points Paolini earns with her forehand more than tripled from previous seasons to 2024. That doesn’t quite account for the entire shift from a top-50 player to a top-fiver, but it explains a whole lot.

And the no-fearhand

One side effect of the Italian’s forehand-centered strategy is that she is less afraid of other players’ forehands.

Again, Paolini is doing just about everything better. For instance, 22% of her first serves went unreturned in 2024, compared with 20% in the past. Nice little boost, but not something you would notice by watching a couple of matches. A bigger shift is where she puts the first serves:

Span     1st Unret%  <=3 W%  RiP W%  D Wide%  A Wide%  
2016-23       20.2%   28.1%   48.3%    25.0%    45.7%  
2024          21.8%   34.8%   53.4%    37.4%    44.8%

Check out the rate at which she is hitting deuce-court first serves wide (D Wide%). 25% to 37% is a massive change, and one that would be dangerous for a different sort of player. In the deuce court, the down-the-tee serve is the conservative one: It goes to the backhand of a right-handed returner, and since it lands in the middle of the court, the returner doesn't have any sharp angles to exploit. The wide serve is the opposite, feeding forehands to opponents like Sabalenka, Rybakina, or Zheng along with the angles necessary to turn them into winners.

What Paolini knows--again, like a savvy doubles player--is that most players will fail to convert the majority of those opportunities, even if they occasionally smack a highlight-reel return winner. The Italian didn't crack the top five by running the table against the elite. Most of her 42 wins came against the next rung of competitors, women who are often held back by inconsistency. Paolini pushed them off the court, giving the choice of either going big (and frequently missing), or sending back a shot that she could handle with her own (improved!) forehand.

All those deuce-court wide serves explain how Paolini picked up so many more plus-one winners (the <=3 W% column) and converted so many in-play returns overall (RiP W%). Every individual wide serve is a gamble, but the Italian has discovered that, on net, they pay off.

The way forward

I'm a bit surprised to find myself concluding that, yes, Paolini might just maintain this level. The odds are heavily against another top-five finish. That was a quirk of her draws and well-timed (probably accidental!) peaks. But 52% of total points? A single-digit year-end ranking? Maybe!

Once I began thinking of the Italian's singles play in terms of doubles strategy, it all clicked. Her anticipation is outstanding--and like everything else, it is better than it was last year. She often wins points without working particularly hard. She's in the right place to end the point on the fifth or sixth shot of the rally. (That place is increasingly at the net. She came to net more in 2024, and she won more of those points than before, too.) Anticipation isn't a skill that will deteriorate with age, nor is it one that opponents can neutralize.

Paolini's new point-shortening, forehand-smacking, deuce-court-serving tactics aren't going to earn her many big upsets, just as they haven't so far. The strongest players--not coincidentally, often the ones with the most fearsome forehands--are the ones in the best position to take advantage the wide deuce-court serves and force the Italian both to move off the baseline and rely more on the backhand.

But a top-ten season doesn't require a pile of top-ten victories. Paolini was 3-6 against that group this year, and that included one win against a fading Ons Jabeur and another in Riyadh against a rusty Rybakina. The Italian's finish owed much more to her 38-15 record against everyone else. Despite the improbability of a top-ten debut at age 28, Paolini has built a game capable of repeating the feat in 2025.

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The Riddle of the Ruud-Rublev Reversal

The story of the the 2024 ATP Tour Finals was the dominance of Jannik Sinner. I’ll refer you to what I wrote after the Australian Open: Yes, Jannik Sinner Really Is This Good. He just passed the 2,300 Elo threshold, becoming only the 12th man since Rod Laver to do so. When I update the Tennis 128 in a few weeks, he’ll be on it.

For all that, I’m preoccupied with something else. On the final day of round robin play, Casper Ruud beat Andrey Rublev to secure a place in the semi-finals. It was their eighth meeting and the Norwegian’s third victory:

Notice anything odd? Take away the unfinished Australian Open tilt, and the head-to-head breaks down precisely on surface lines. Rublev has won all four encounters on clay, while Ruud has run the table on hard courts. Not just any hard courts: indoors, at the Tour Finals.

We can look to external factors to explain some of the individual results. Casper had more at stake on Friday than the Russian did, with a chance to qualify for the final four. Rublev is older and broke through correspondingly earlier, so he was the natural favorite in their early meetings. Injuries and illness may have influenced another outcome or two, even aside from the retirement in Melbourne.

Still: 0-3 in completed matches for the ball-basher on hard courts, and 0-4 for the Roland Garros finalist on clay. Something’s going on here.

Not so fast

Rublev, to be fair, is hardly a fast-court specialist. His first tour-level title came on dirt in Umag, and he picked up a Masters crown last year in Monte Carlo, on one of the circuit’s slowest surfaces. The Russian’s forehand is a weapon in any conditions, and slow courts can disguise some of his weaknesses.

On the other hand, however much Rublev likes the dirt, Ruud likes it more. Earlier this year, I quantified the notion of “surface sensitivity,” the degree to which a player’s results are influenced by court speed. Rublev scored at -2.2, indicating that he does better on slower surfaces, a bit more so than the typical tour regular. Casper was considerably further down the list, at -5.0. The rating tells us that he’s more receptive to slow courts than Pablo Carreno Busta or Jaume Munar. He’s grades about the same as Diego Schwartzman.

Maybe the oddball head-to-head is a quirk of when the pair have met? Not all hard courts play fast, and not all clay behaves like the crushed brick at Roland Garros. Here are the venues for the seven completed meetings, along with my ace-based surface speed rating for each. Ratings above 1 are faster than average, below 1 are slower:

Year  Tournament   Winner  Speed  
2024  Tour Finals  Ruud     1.36  
2023  Bastad       Rublev   0.86  
2022  Tour Finals  Ruud     1.50  
2021  Tour Finals  Ruud     1.51  
2021  Monte Carlo  Rublev   0.54  
2020  Hamburg      Rublev   0.52  
2019  Hamburg      Rublev   0.74

Hypothesis denied! The 2021 and 2022 Tour Finals were the fastest conditions of their respective years, while Monte Carlo was the slowest of the entire 2021 season. Last year’s Bastad surface was fairly neutral for a clay court, but the rest of the Ruud-Rublev showdowns took place on fast hard courts or slow clay.

We could always mark down a string of seven surface-confounding results to luck, especially when both players are capable in all conditions. But it would be far more satisfying to find an explanation that tells us something about the players and their particular skills.

Stoppable

We don’t have to look far. Here are Casper’s win rates on first and second serve points against Rublev, separated by surface:

Surface  1st W%  2nd W%  
Clay      56.8%   48.4%  
Hard      72.7%   50.7%

Everybody wins fewer first serve points on clay than on hard courts, but not like this. The average gap for top-50 players in 2024 is four percentage points–not sixteen. At tour level against the entire field, Ruud has shown an even smaller difference, winning 73.1% of hard-court first-serve points against 71.2% of those on clay.

Rublev is not a brilliant returner. He’s a serviceable one with tactics to match. He often struggles to get first serves back in play. On second serve, he’s unafraid to unleash his weapons, accepting some errors in exchange for tilting other points in his favor. On clay, he’s able to turn a few more first serves into rally openers. In 2024, his gap between clay and hard-court first-serve return points won was bigger than average. But not nearly as wide as it is against Casper.

When it works…

Ruud, like many men who have developed into strong clay-courters, doesn’t have a monster serve. He can place it, he can disguise it, and he knows how to play behind it. On a fast hard court, those skills–combined with a bit more risk-taking–can result in numbers that look more like those of a big server. Against Rublev last week, he won just shy of 80% of his serve points, supported by 15 aces.

When the Norwegian is hitting corners and the ball is skimming off a court like the speedy one in Turin, Rublev is helpless. Over his career, according to the nearly 200 matches logged by the Match Charting Project, he puts 58% of first serves back in play. Against Casper on Friday, he didn’t manage 50%–a repeat of his performance on the same court two years earlier.

Rublev’s first-serve-return struggles on hard court contrast with how he feasts on Ruud’s serve on clay. The next table shows the rate at which the Russian puts Casper’s first serves in play, as well as his win percentage when he does so:

Match                Result  1st: RiP%  RiP W%  
2024 Tour Finals RR       L      46.9%   43.3%  
2023 Bastad F             W      64.6%   61.3%  
2022 Tour Finals SF       L      45.7%   50.0%  
2021 Tour Finals RR       L      67.5%   51.9%  
2021 Monte Carlo SF       W      84.4%   59.3%  
2020 Hamburg SF           W      91.4%   59.4%

The exception to the rule here is the 2021 Tour Finals match, which ended in a third-set tiebreak. It was the closest either man has come to securing one of the matches he “should” have won. Rublev won 52.9% of total points, but Ruud served his way out of just enough jams to come through.

On the very slow Monte Carlo and Hamburg courts, Rublev’s ability to handle the Norwegian’s first serve meant that Ruud was left with no edge whatsoever. Casper might be the superior baseliner, but he started too many points at a disadvantage. The picture might look different if they played on slow clay today, since Ruud is stronger and tactically savvier on serve. But I imagine it would still be a struggle, one in which few of Casper’s service games would sail by quickly.

Pundits like to say that tennis is a game of matchups. They often overstate their case: The better player (by ranking, or Elo rating, or whatever) usually wins. When they don’t, it isn’t always because of some quirk in the head-to-head. With Rublev and Ruud, though, such a quirk dictates the results. Few men are able to erase Rublev’s advantage on a hard court as much as the Norwegian can. Casper’s first serve is rarely so ineffectual as when the Russian is waiting for it on dirt. Ruud is set for another big European clay swing next year–so long as his buddy Andrey lands in the other half of the draw.

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