Jakub Mensik, Giant Killer

Watch out

On Saturday, Jakub Mensik did it again. Jack Draper was coming off an Indian Wells title, the fortnight of his career, but Mensik was a little bit better. Both sets went to tiebreaks, and twice, at six-all, the 19-year-old Czech took his serving to a new level. He won 14 of 19 tiebreak points and sent the Brit home early.

After such an assured performance, Mensik’s third-rounder felt like a gimme. Roman Safiullin gave him two looks at break points, and that’s all he needed. Behind another monster serve barrage, the Czech waltzed into the fourth round, 6-4, 6-4.

Mensik currently stands outside the top 50, but his ranking doesn’t tell the full story. For one thing, he made his top-50 debut late last year, and his Miami points will almost certainly be enough for him to return. Beyond that, he has proven that he fears no one on tour. Draper was his 6th top-ten win in 11 tries. What’s more, Mensik won a set in three of the five losses, including a meeting in Shanghai last fall with Novak Djokovic.

Djokovic called him “one of the best servers we have in the game.” Indeed, since the US Open last year, the six-foot, four-inch Mensik is cracking aces on more than 15% of his serve points. Only Giovanni Mpetshi Perricard and Quentin Halys rate better among tour players. He has taken things to a new level in Miami. In each of his three matches–against Roberto Bautista Agut, Draper, and Safiullin–he has hit an ace on at least 26% of his serve points. That’s Reilly Opelka-level serve dominance, and even Opelka hasn’t posted three straight ace rates like that since 2022.

Mensik is one of the most exciting prospects on tour, yet Joao Fonseca-mania doesn’t leave much attention to anyone else. What do we make of those top-ten wins… and the non-top-ten losses that have kept him on the edge of the top 50? How should we rate the rest his game–you know, those occasions when he doesn’t end the point with a first serve? Let’s dig in.

Proof of concept

Here is the top-ten record:

Pretty good for someone with another five months left in their teens.

Draper wasn’t the first top-tenner that Mensik overpowered. In the six wins, the Czech held serve 90% of the time, winning three-quarters of first serve points. Djokovic and Alex de Minaur figured out how to neutralize the serve, but lesser returners (read: most other humans) have not.

Even before the Miami upset, Mensik was just the 21st player since the beginning of the ATP rankings to win at least five of his first ten meetings with top-tenners. (I’m excluding players who were already established in 1973, when the points table debuted.) He’s just the 12th ever to win six of eleven. Here’s the full list:

Player               First 10  First 11  
Alberto Mancini           7-3       7-4  
Miloslav Mecir            7-3       7-4  
Fernando Gonzalez         6-4       7-4  
Marc Kevin Goellner       6-4       7-4
Lleyton Hewitt            6-4       6-5  
Jakub Mensik              5-5       6-5  
Ugo Humbert               5-5       6-5  
Marcos Baghdatis          5-5       6-5  
Marat Safin               5-5       6-5    
Carlos Moya               5-5       6-5  
Chris Woodruff            5-5       6-5  
Magnus Larsson            5-5       6-5  
Boris Becker              5-5       6-5  
Fabian Marozsan           5-5       5-6  
Aslan Karatsev            5-5       5-6  
Matteo Berrettini         5-5       5-6  
Reilly Opelka             5-5       5-6  
Mardy Fish                5-5       5-6  
Nicolas Kiefer            5-5       5-6  
Henrik Holm               5-5       5-6  
Greg Holmes               5-5       5-6

It’s a strong list, if a bit scattershot. We have all-time greats, plus Aslan Karatsev and Greg Holmes, who apparently upset both Mats Wilander and Jimmy Connors. The playing styles might tilt a bit toward heavy hitting and big serving, but not overwhelmingly so.

I mention playing styles because rocket serves, like Mensik’s, have a way of turning matches into coin flips. If the serves aren’t coming back, it doesn’t matter how well the guy returns. Other skills fall by the wayside: We’re headed for a tiebreak. Apart from a pair of early breaks, that’s what happened in the Draper match. John Isner won three of his first ten top-ten encounters, and Opelka earned a spot on this list.

Everything else

When the serves do come back, though, it’s anybody’s ballgame, top-ten opponent or not. For Mensik, just about everything apart from the first serve is a relative weakness. In the last 52 weeks, he has won just 47.4% of his second-serve points, worse than 49 of the top 50 players. (Pedro Martinez is the one guy with a sub-Mensik number.)

The Czech has gotten accolades for his backhand, but it’s not really a weapon. While it doesn’t hold him back, it rates about tour average by my Backhand Potency (BHP) metric. His Forehand Potency is the real issue. At just +1.1 per 100 forehands, he ranks ahead of only a few of his colleagues, including Opelka, Mpetshi Perricard, and Hubert Hurkacz. Hurakcz has proven that it’s possible to hang around the top of the game without much help from the forehand, but it’s a narrow path to follow.

All this adds up to some painful numbers in rallies. I was going to say “long rallies,” but Mensik starts to see a disadvantage about as soon as the word “rally” comes into play. In eleven charted matches over the last 52 weeks (not counting the Draper upset), here are how his results shake out by rally length:

Length      Win%  
1-3 shots  52.2%  
4-6 shots  45.3%  
7-9 shots  41.9%  
10+ shots  42.0%

52% on short points is great! That was enough to crack the top ten list when I looked at the same category last week in the context of Draper’s excellence. Since these stats encompass both serve and return, it tells us that he’s cleaning up more of his own quick points than his opponents can manage of their own.

The rest of the story, though, is bleak. He ranks near the bottom in all three of the other categories. If we lump them together, he win the fewest points of anyone with at least ten charted matches in the last year:

Player              1-3 W%  4+ W%  
Jakub Mensik         52.2%  43.8%  
Mpetshi Perricard    51.6%  43.8%  
Zhizhen Zhang        48.5%  44.1%  
Jiri Lehecka         51.8%  44.2%  
Ben Shelton          50.5%  44.7%  
Hubert Hurkacz       55.0%  45.4%  
Lorenzo Sonego       52.5%  45.5%  
Tallon Griekspoor    49.8%  46.1%  
Flavio Cobolli       44.9%  46.6%  
Alexei Popyrin       50.4%  46.8%  
…                                  
Jack Draper          53.3%  48.8%  
…                                  
Stefanos Tsitsipas   50.5%  50.6%  
…                                  
Alexander Zverev     53.0%  53.1%  
…                                  
Novak Djokovic       53.7%  54.9%  
Carlos Alcaraz       52.5%  55.8%  
Jannik Sinner        54.4%  57.0%

Somehow, it gets even worse. With enough short points, weak long-rally skills are survivable. Yet Mensik plays more long points than most of these guys in the bottom ten. The 1-to-3-shot category accounts for less than 63% of his points, while it makes up more than 70% of Mpetshi Perricard’s. Even Jiri Lehecka, hardly an extreme case like GMP, comes in at 66%.

Second to last

Mensik is hardly an elite returner, but he is good enough for now. He has won about 37% of his return points over the last 52 weeks, a rate that–coupled with strong serving–is sufficient to get him into the top ten. Despite his relatively low ranking, he has posted those numbers against high-quality competition. His median opponent has been stronger than those faced by Stefanos Tsitsipas or Casper Ruud.

The immediate concern for the Czech is his second serve. I mentioned earlier that he wins barely 47% of those points. Ben Shelton, who wins exactly as many first-serve points as Mensik does, converts 55% of his seconds. While that’s unusually good, nearly every player in the same first-serve territory wins at least 51% behind the second serve.

This is a good time to remember that Mensik is 19. He hasn’t been six-foot-four for long. It’s possible that his second serve will look entirely different in two years than it does today. He’ll certainly hope so. He misses more than 12% of his seconds, a double-fault rate that would be acceptable only if he were taking chances and reaping the rewards of those risks. At the moment, he’s just struggling.

The second-serve weakness is more than enough to flip the outcome of a match. In the last year, when Mensik has landed at least 60% of his first serves, his record is 16-5. Under 60%, it’s 12-17.

The root of the problem is what happens when the second serve comes back. The Czech’s second delivery isn’t yet strong enough to generate many easy plus-one opportunities, and his ground game isn’t sturdy enough to make up for it. When his first serves come back, his results are close to tour average. But when the second serve comes back, he ranks at the very bottom of the table.

This scatterplot shows every player with at least ten charted matches over the last year. It compares each player’s win rate when their first serves come back with their results when second serves come back. Guys below the dotted line see relatively worse outcomes behind their second serve:

There’s no single limitation that is depressing Mensik’s second-serve results. The positive spin on that is that he has a lot of areas with room to improve. Even an average second serve–seemingly a reasonable goal for a man with such an imposing first–would probably make him a top-20 player.

The way forward

Nothing makes it easier to dream about a big future in tennis than a monster serve. Any list of overrated youngsters is going to be littered with powerful teens who remained too one-dimensional to convert all their aces into tournament victories.

That, I think, is the low-end forecast for Jakub Mensik. If he simply keeps doing what he’s doing, he could be a top-40 or top-50 player for a long time. His first serve is that good, and the rest of his game is adequate. He probably wouldn’t continue to win half of his top-ten meetings, since the game’s top players would have more time to figure him out.

On the other hand, again, he’s 19! The difference between his first- and second-serve results is a statistical oddity, which could mean either that he is uniquely one-dimensional, or that he has plenty of room to develop. The latter seems more likely. He may remain limited on return, but a second serve to match his first would make him near-unbreakable. That’s the recipe for a lot more top-ten wins, and possibly for a single-digit ranking of his own.

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Are Second Serves Mostly Useless?

Novak Djokovic loading up for some topspin

During the Australian Open, Challenger player (and Youtube star) Karue Sell made a bold statement:

Thank you, Karue, for posting this: It is always valuable to get specific claims about the game from the people who are trying to figure out how to win. Right or wrong, testable propositions like these help nudge our understanding in the right direction.

Now: Right or wrong?

Are second serves becoming mostly useless? A first look at the data says no–or, at least, they aren’t becoming any more useless than they were before. Here is second serve win percentage for tour-level matches since 1991:

The important thing here isn’t the trend. It’s the narrowness of the values. The difference between the lowest and highest ticks on this graph is only three percentage points, and half of that happened before the century turned. Strength and strategy may be different–we’ll get to that–but the results aren’t. If anything, second serves have become (modestly) less useless.

This trend holds up even when we tweak the parameters. Yes, the surface mix of the tour has changed since the 1990s. But if we look only at hard-court matches, there’s an even tighter range of yearly averages, between 48.9% and 51.2%. At Sell’s Challenger level, I only have data back to 2010. In that span, hard-court second-serve win rates have drifted less than a single percentage point, between 49.7% and 50.6%.

I can’t help but notice that Sell’s own Challenger-level second-serve win percentage is a healthy 52%. I’m sure it sometimes feels useless: The last match he played before making the comment was a qualifying-round loss in which he salvaged less than 40% of second-serve points. But despite his relatively small stature, he won more main draw second-serve points last year than Matteo Berrettini did–albeit against weaker competition.

Risk and reward

No one wants to settle for historical average. Inevitably, someone brought up the notion of two first serves:

No, two first serves are not the way. But Sell recognizes what might work. At least in theory, players should take more risk on second serves (and perhaps on firsts, as well), hitting bigger and winning more points at the cost of more doubles.

If tennis trends proceeded by opinion poll, I think we’d already see evidence of this. I certainly never see anyone argue that players should be more conservative with the second ball, unless they’re talking about a particular struggling player. But all that matters is what happens on court, and there’s no sign there of more double faults:

Again, the framing doesn’t matter. The numbers are about the same regardless of surface, and Challenger players have moved in the same direction. In fact, the 2025 Challenger rate so far is 9.8%, the first time that the minor leaguers have dipped below double digits.

To be clear, I wouldn’t expect any sudden moves here. A generation of players grows up learning certain serves and tactics, and there’s only so much they can do to change them. An equation might spit out that someone would win, say, 56% of second-serve points in exchange for accepting a 12% double-fault rate. But do athletes really have such fine-grained control of the risks they take? I suspect not, which means another generation may go by before we see a true “1 and 1.5” strategy.

Is 100 miles per hour a must?

How fast do second serves need to be? While I can’t imagine any player would turn down a triple-digit average, we’re nowhere near that level. The rightmost column shows the average second-serve speeds at the 2024 US Open for every player who reached the third round:

Only 4 of 32 averaged triple digits. Just five posted a mark at or above 96 miles per hour. The dominant tournament winner, Jannik Sinner, barely topped 90.

It’s possible that the sensors (or the balls, or the humid conditions, or pick your variable) resulted in low readings: US Open speeds are typically several miles per hour lower than Wimbledon speeds, even for the same players. But the gap isn’t enough to push more than a quarter of these guys over the magic number.

Still, Sell could be correct on the trend, if not on the detail. Maybe second serves are getting faster, or slower second serves are more likely to end in a point lost.

US Open data, though, suggests that second serves have stayed about the same. I have relevant data back to 2014, plus 2011. Splitting second serves into buckets of 100-plus miles per hour, 95-99, 90-94, and so on, it’s tough to find much of a trend:

(In case you’re wondering, the 2012-13 data has serve speeds, but no indication of first or second serves. Not very helpful here!)

Same story with win rates. As with the tour in general, the US Open has seen a steady percentage of second-serve points won. The next graph shows year-by-year win rates both overall and for the 85-89 mile-per-hour bucket, on the theory that if returners were feasting on relatively weak seconds, it would show up there:

While the 85-89 mph results are noisy, there’s not much to see here. The overall win rate in 2024 is almost identical to what it was 13 years earlier. There’s a bit of space between 85-89 mph second serves in 2011 and 2024, but still not much.

It’s certainly true that harder is better, and that hasn’t changed. At every one of these US Opens, the win rate of 100-plusses exceeded the win rate of sub-85s by at least five percentage points, and the gap rose as high as ten points at the 2020 Covid event. But we’ve yet to find much evidence for the notion that second serve speeds or results are any different than they were 10, 13, or even 30 years ago.

Are servers going to the forehand more often?

Finally, we can say… maybe?

I pulled all hard court matches since 2014 between right-handers from the Match Charting Project database. (Hard court, because it’s so much easier to run around second serves on clay; 2014, because that’s when the project started, so there’s not as much bias toward big-name players and matches; right-handers, because lefties, while fascinating, make things way more complicated.)

The charts classify serves into three categories: Wide, body, and T. Second serves to the “body” usually aren’t good: Those are serves that didn’t find a corner. In the men’s game, that’s 35-40% of seconds. It’s tough to tell from the chart–and sometimes even when watching a match–exactly which side the server targeted, because it is so easy for the returner to take a step or two around it and hit a forehand.

Servers are indeed more likely these days to find the forehand corner:

This isn’t an enormous move, but it seems like a real thing. If we throw out the 2020 Covid season, it would look like an even more dramatic shift just in the last few years.

However, more second serves to the forehand corner does not mean fewer second serves to the backhand corner. These extra forehand-targeted serves are coming at the expense of the mediocre “body” seconds. Servers drill the backhand corner 30% to 35% of the time, and that range hasn’t budged over the last decade.

I’d more inclined to say, then, that players have gotten a bit better. And they’ve chosen to use that improvement to keep returners off balance, aiming a few more second serves to the forehand side.

Are players too good from the back?

Sell’s theory is that more second serves are targeting the forehand, because the backhand is no longer such a weak side. We can use the same subset of MCP data to check how (right-handed) returners have fared against second serves to their backhand corner:

Again, 2020 is weird; other than that, we’re just looking at noise. (Or, possibly, the signature of a drunk blue M&M.) The long-term average of this stat is 50.6%, and in ten of the twelve seasons, the single-year number was within half a percentage point of that.

Backhand returns may have gotten stronger, but if so, serves are advancing at the same rate.

What gives?

Why would Karue identify trends that, for the most part, have so little evidence to support them?

First, the tour is getting stronger, at backhand returns and everything else. Some serves that would’ve gone unreturned in 2005 or 2015 are coming back today. As we’ve seen, servers are maintaining a balance. But it’s easy to suffer a few bad results and conclude that drastic changes have taken place.

Second, Karue himself played his best tennis last year. He cracked the top 300 for the first time and played a dozen Challenger main draws. That meant he faced stronger competition than ever. The Challenger tour is full of baseline battlers with sturdy backhands; there isn’t a huge gap between the return skill that Sell faces these days and the elite-level returning we watch on TV. Moving up from ITFs to Challengers means that some weapons don’t work anymore, and–especially for smaller guys–new tactics are needed.

I’d love to see Sell, or anyone else, give a serious trial to the “1 and 1.5” serve strategy. Hit seconds harder, attack the forehand more often, and accept more double faults. Karue might be right about what the future of second serves will look like, but we’re not there yet.

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The Inscrutable Magic of Jessica Pegula

Jessica Pegula playing defense at the 2022 US Open

Alright, alright, alright.

When I started writing these player-themed pieces more than a year ago, Jessica Pegula was at the top of my list. One of my goals is to demystify the factors that cause each player’s success, or lack thereof. Pegula has had plenty of success, but compared to her peers at the top of the game, it is difficult to say exactly why.

There’s no obvious calling card that intimidates opponents. Pegula doesn’t serve very hard, ranking in the middle of the pack at least year’s US Open with an average serve speed around 92mph and first serves at 99mph. She doesn’t hit many aces. She ranks just outside the top ten in hold percentage, largely because she cleans up on second serves. That’s her one standout, top-line stat: In the 52 weeks leading up to Indian Wells, she won 51% of second-serve points. Only four women have topped 50%, and only Iga Swiatek wins more.

Pegula’s return numbers are even more anonymous. She ranks 20th among the WTA top 50 in break percentage. Top 20 on both sides of the ball is outstanding and unusual, but again, hardly intimidating. Whether serving or returning, she isn’t particularly effective on break points. Not that she’s bad in that department, but clutch play doesn’t help us understand all the match wins.

But win matches she certainly does. The American has held a place in the top ten since June 2022, much of that time in the top five. She has won seven tour-level titles and reached finals at both the US Open and the year-end championships. Off a title in Austin, she’s on a seven-match winning streak going into today’s match against Elina Svitolina. Elo isn’t quite as excited about her performance, but even that metric places her seventh, only 16 points behind fifth-place Qinwen Zheng.

What, then, is Pegula doing so right? When a player gets better results than her tools seem to suggest, I tend to fall back on difficult-to-quantify assets like movement, anticipation, and the blackest box of all, tennis IQ. Pegula excels in all those categories. But can we do better?

Second thoughts

Let’s start with the second serves. Here’s a generic theory for you: second-serve win percentages are related to success rates on return. Few women have dominant second serves–remember that Pegula is one of only a handful who win more than half of those points–so especially if the returner puts the ball in play, the server is already on defense.

Indeed, there’s something of a relationship, though not a statistically strong one. This plot shows the WTA top 50 in both categories:

jpeg.jpg

Here’s a sentence I didn’t expect to write: Pegula and Sabalenka are almost identical in this pair of metrics. To go a step further, the cluster of players extending from Alexandrova in the lower left, to Sabalenka, then to Swiatek in the upper right, is disproportionately made up of big hitters. (The finesse players, along with the always unpredictable Jelena Ostapenko, are in the lower right.)

Yet by the standards of women’s tennis in the 2020s, Pegula is not a big hitter. It’s natural enough that she would equal Sabalenka’s return results, even if they get there in different ways. But second serves, too?

After watching Pegula’s quick dismissal of Xinyu Wang on Sunday, I thought I had the answer. While her second serves aren’t fast (79mph on average at last year’s US Open), they are precise. She doesn’t tee them up down the middle, and she manages to hit targets close to the service line. Location can be as valuable as raw speed, so that might explain how she gets the results of a bigger server.

Except… I can’t prove that she does any of that on a consistent basis. US Open scorers classify serve depth as “close to the line” or “not close to the line. Pegula merited a “close to the line” designation on 15% of her second serves, compared to a tournament average of 18%. She was slightly below average on first serves, too.

As for serve direction, it’s the same story. The Match Charting Project classifies each serve as one of three directions: wide, body, or down-the-tee. The average server hits one of the corners (wide or tee) with about 80% of their second serves. Pegula’s number is 74%. That’s not in itself bad–Venus Williams sports the same number–but it certainly doesn’t support my theory.

If there’s a quantifiable reason why Pegula wins all those second-serve points, it doesn’t look like we’ll find it in the second serve itself.

The match and the territory

Another eye-test hypothesis about Pegula: She doesn’t wait for the game to come to her. She stands as close to the baseline as she can get away with, both returning serve and in rallies. She doesn’t back up when faced with a deep drive or a high bounce. Depending on the shot, she’ll pick it up on a short hop or reach above her shoulder.

Not everyone is able to do this. For those who can, the advantages are clear. The earlier you hit the ball, the faster it gets back in your opponent’s court–and the less time they have to react. It’s power tennis for women without overwhelming power.

This style of play is particularly effective against opponents who aren’t particularly aggressive. Pegula’s losses this year have come against Madison Keys, Olga Danilovic, Ekaterina Alexandrova, and Linda Noskova: a quartet of heavy hitters who end points fast. Pegula lost just two matches on North American hard courts last summer, both to Aryna Sabalenka.

Against less free-swinging foes, the American takes away chances. Pegula doesn’t hit an overwhelming number of winners: 6% of her groundstrokes go untouched, in line with tour average. But her opponents do worse. In the Austin final, McCartney Kessler scored winners on just 2% of her shots from the baseline, half her usual rate. Pegula applied the same pressure to Xinyu Wang Sunday, slashing the Chinese player’s groundstroke-winner rate to 4% from a career average of 7%.

Again, these are stats that invoke parallels with a different style of player. The best way to prevent winners is to hit winners of your own, or at least end the point trying. That’s the Keys/Alexandrova/Ostapenko/etc playbook. Yet by Aggression Score, a metric that puts those ball-bashers on top, Pegula is below average, keeping company with the likes of Emma Navarro and Mirra Andreeva.

Deep research

Maybe you’re convinced that this explains a lot of Pegula’s success. She hugs the baseline, cuts off angles, and takes away opportunities for all but the most aggressive players to find openings of their own.

Still, I’d like more support from the numbers. Positioning is tricky to quantify, so I want to focus on one specific situation. What happens when the American is faced with a very deep service return?

Deep returns essentially erase the server’s advantage, neutralizing the point with one swing. The server usually needs to take a step or two back, and unless it’s a perpetual gambler like Ostapenko, she won’t try anything flashy for at least one more shot. Pegula doesn’t aim to end the point, either, but she’s less likely to concede territory. While that doesn’t allow her to seize the advantage, she’s careful not to hand too much of an edge to the returner.

Yet… nope. The next table shows how the ten players with the most hard-court data since 2022 handle deep second-serve returns: How often they get the next ball back in play (“3rd-inPlay”), how often those balls in play result in points won (“inPlay W%”), and how often they win points against deep returns, even considering the ones they didn’t get back (“vsDeep W%”).

Player            3rd-inPlay  inPlay W%  vsDeep W%  
Iga Swiatek            84.2%      59.8%      50.4%  
Aryna Sabalenka        77.5%      63.5%      49.2%  
Karolina Muchova       84.2%      56.3%      47.4%  
Paula Badosa           84.2%      54.6%      45.9%  
Elena Rybakina         79.5%      57.5%      45.7%  
Daria Kasatkina        85.5%      52.2%      44.6%  
Coco Gauff             83.6%      53.2%      44.5%  
Jasmine Paolini        82.7%      53.7%      44.4%  
Jessica Pegula         81.9%      53.2%      43.6%  
AVERAGE                81.8%      53.0%      43.4%  
Qinwen Zheng           76.5%      52.6%      40.2%

Pegula is almost exactly average, which makes her less effective against deep second-serve returns than most other top players. (The average considers all players, not just those listed, which is why it’s so close to the bottom.) Sticking to the baseline might still be the best solution for her, but it doesn’t win her an unusually high number of points.

This is a lot of negative results for one post. Pegula is close to the best in the business at turning her second serve into points won. But it’s not because she hits her seconds deep, or because she keeps the ball away the returner, or because she handles deep returns unusually well.

So we’re more or less back where we started. The American does a lot of things well, or at least well enough that they are not liabilities. Among top 50 players, she is average or better in nearly every category, close to the top ten in a few. By my groundstroke potency metrics, FHP and BHP, she does even better: She ranks among the top 20 in both, one of the few players to do so.

That, apparently, is good enough for a place in the top five. With better, finer-grained stats, we might be able to isolate how Pegula turns court position into victory. For now, we can appreciate how she holds her own against opponents with more fearsome weapons. Her personal brand of flexible shotmaking is certainly working, whether we understand it or not.

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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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