Net play – Heavy Topspin

Visualizing Trends in Net Play Across Five Decades of Grass Court Tennis

Earlier this week, I wrote about one aspect of the long-term decline in net play: the widespread belief that approaching the net is more difficult now because fewer players have a weaker side. I presented evidence indicating that most players still have a weaker side, which suggests that all groundstrokes–on both strong and weak sides–have gotten stronger, making net play a riskier proposition.

If that is true, it is reasonable to assume that passing shot winners are more frequent (relative to the number of net approaches), and perhaps that volleys are more aggressive, resulting in more first-volley winners and first-volley errors. More powerful and precise strokes should, on balance, make net points shorter than they used to be.

We can begin to test these theories using the extensive shot-by-shot records assembled by the Match Charting Project (MCP). MCP data includes every men’s Wimbledon final and semi-final back to 1990, as well as many elite-level grass court matches from the 1970s and 80s. For the purposes of today’s study, I will use only Wimbledon semi-finals and finals, plus a handful of other grass court matches from 1970-89 to complement the sparser Wimbledon data. This way, we know we’re comparing the elites of various generations to one another.

Contemporary net approaches

Let’s start by looking at what happens in a 2010s Wimbledon’s men’s final or semi-final when a player approaches the net. I’m excluding serve-and-volley points, and will do so throughout. I’m also excluding approach shot winners, which are often little more than gestures in the direction of the net following a big shot. (Even when they’re not, it can be difficult for charters to distinguish between approach and non-approach winners.) Thus, we’re looking at about 1,250 net approaches in which the other player got his racket on the ball.

The ball came back almost 73% of the time, and on slightly more than half the points, the approaching player put his first volley (or smash, or whatever shot he needed to hit) in play. 19% of the points saw a second passing shot attempt put in play, and nearly 12% had a second net shot keep the point going. About 1 in 30 approach-shot points continued even longer, forcing the the netman to contend with a third pass attempt.

The following visualization is a Sankey diagram showing how these net points developed. “App” stands for approach, “Unret” for “unreturned,” “Pass1” for “first passing shot,” “V1” for “first volley,” and so on. Mouse over any region of the diagram for a brief summary of what it represents.

There’s a lot of information in the graphic, and it may not be entirely intuitive, especially hindered by my clunky design. Each region is sized based on what fraction of points developed in a certain way. As the regions move toward the right side of the diagram, they as classified by whether the approaching player won the point. As we can see, in the 2010s sample, these approach shots resulted in points won about 69% of the time.

The golden era

To compare eras, we need more than just one decade’s worth of data. I separated the approach shots by decade (grouping together the 70s and 80s), and the most distinctive era turned out to be the 1990s, when Pete Sampras ruled the roost and many of his challengers were equally aggressive.

Far more points were opened with a serve-and-volley: almost 81% in the 1990s compared to 7% in this decade. Even with the server claiming the net so early and so often, there were still many more non-serve-and-volley net approaches two decades ago. Then, there were about 85 “other” net approaches per match; this decade, there have been about 27. Thus, it is reasonable to assume that the typical net approach started from a less favorable position. These days, players only approach when the point has developed in a particularly inviting way.

Here is another diagram, this one showing what happened following 1990s net approaches:

It’s striking to see that, back when net play was much more common, with a master such as Sampras dominating our sample, net approaches were less successful than they are today, resulting in a 67% win rate instead of 69%. However, it’s tough to know how today’s players–even a confident aggressor like Roger Federer or a volleying wizard like Rafael Nadal–would fare if they came forward four times as much. Assuming they pick their spots wisely, their success rate would be lower than 69%. The only question is how much lower.

Contrary to my inital hypothesis, passing shots seemed to be higher-risk and higher-reward in the 1990s than in the 2010s. Two decades ago, only 65.5% of initial passing shot attempts were put in play (compared to 72.6% today), though nearly as many of those attempts resulted in winners (21.1% to 21.4%). It was the volleyers who were either more conservative or less powerful in the 1990s. Then, barely half of first volleys ended the point in the netman’s favor; now, the number is closer to 60%. Again, this could be because today’s players pick their spots more carefully, allowing them to hit easier first volleys.

The early days

We’ve seen how net approaches developed in the 1990s and the 2010s. It would be reasonable to assume that the 1980s (with several late ’70s matches thrown in) were like the 1990s, but more so. Instead, the results are more of a mixed bag, with some characteristics that look like the ’90s, and others that are closer to today’s numbers.

Here is the diagram:

In the 1980s, nearly as many passing shot attempts were put in play as they are today, in contrast to the lower rate during the 1990s. First volleys are a similar story. When passing shot attempts came back, approaching players put a volley (or other net shot) back in the court about 70% of the time–similar numbers in the 1980s and 2010s, but a couple percentage points higher than in the 1990s.

What is different is what happened next. In the 1980s, if the approaching player put his first volley back in play, it came back again 53% of the time. That rate is one of the few clear trends over time: It fell to 46% in the 1990s, 45% in the 2000s, and 37% in the 2010s. As a result, the ’80s saw far more second volleys and points that extended even further, compared to more recent eras. The lack of first-volley putaways meant that net approaches only converted into points won about 65% of the time.

A cautious narrative

There is no simple explanation that accounts for all of these numbers, because we are not seeing the direct result of a single factor, like the shift from wooden rackets or to more topspin-friendly string. Technological changes certainly have an impact, but as soon as the balance between approacher and opponent shifts, players adjust their strategy accordingly.

For instance, the rate of points won on net approaches appears to have steadily increased, from 65% in the 1980s to 67% in the 1990s to 69% today. The first rise could be attributed to racket technology, which gave aggressors more power and control. But the second rise came over a time period in which string technology offered more help to defenders. The higher rate of approach points won isn’t because players are better at it, it’s because they picked their spots more carefully.

What we might focus on instead, then, is how much these diagrams look alike, even though they represent vastly different eras. While there isn’t exactly a net-approach-strategy equilibrium that has held through the decades, player decision-making has kept these rates from varying too wildly. If passing shot winners start going up, we’ll probably see even fewer approaches–with the remaining approaches in still more favorable moments–or a continued increase in the percentage of approaches to the backhand side. That’s another clear trend over the last few decades, but it’s a topic for another day.

Rather than succumbing to nostalgia and bemoaning the decline of net play, it’s better to celebrate the adaptability of tennis players at the highest level. While the game a whole has become more defensive, backcourt denizens from Bjorn Borg (94 approaches per charted grass-court match) to Novak Djokovic (21 approaches per match) have reminded us that adjustments work in both directions. With parameters such as technology, surface, and opponent skills constantly changing, we can’t expect winning strategy to remain the same.

Thanks to SankeyMATIC for making it easy to create the diagrams.

Net Play Has Declined, But This Isn’t Why

Italian translation at settesei.it

Wimbledon is here, so it’s time for another cycle of media commentary about the demise of net play, especially the serve-and-volley. The New York Times published a piece by Joel Drucker last week that covered this familiar territory, cataloguing various reasons why the game has changed. Racket and string technology, along with tweaks to the All England Club playing surface, are rightfully on the list.

But the first reason Drucker gives is the rise of the two-handed backhand and, by extension, the threat posed by players with weapons on both sides:

In May 1999, 43 of the top 100 male players in the world hit their backhands with one hand. As of June 2019, there were 15. According to Mark Kovacs, a sports science consultant and tennis coach, “Most players used to have a weaker side, usually the backhand. And the two-handed backhand changed that completely. It doesn’t give you a spot you can hit to.”

I’m more interested in the “weaker side” argument than the fortunes of the one-handed and two-handed backhands. Many players who still use one-handers, such as Stan Wawrinka, would rightly bristle at a claim that their shots are weak. In terms of effectiveness, the contemporary one-handed shot might have more in common with a two-hander of old than the all-slice, only-defensive backhand favored by many pros in the 1970s and 1980s.

Both sides, now

The “weaker side” argument can be slightly rephrased into a research question: For contemporary players, is there a smaller gap between forehand effectiveness and backhand effectiveness than there used to be?

To answer that, we need a working definition of “effectiveness.” Long-time readers may recall a stat of mine called “potency,” as in “backhand potency” (BHP) or “forehand potency” (FHP). It’s a simple stat, using data derived from the shot-by-shot records of the Match Charting Project, calculated as follows:

BHP approximates the number of points whose outcomes were affected by the backhand: add one point for a winner or an opponent’s forced error, subtract one for an unforced error, add a half-point for a backhand that set up a winner or opponent’s error on the following shot, and subtract a half-point for a backhand that set up a winning shot from the opponent.

The same procedure applies to forehand potency and slice potency. The weights–plus one for some shots, plus a half point for others, and so on–are not precise. But the results generally jibe with intuition. Across 3,000 charted ATP matches, an average player’s results from a single match are:

Forehand potency (FHP): +6.5
Backhand potency (BHP): +0.8
Slice potency (SLP): -1.3
Backhand side potency (BSP): -0.5

The first three stats isolate single shots, while the final one combines BHP and SLP into a single “backhand side” metric. All of these exclude net shots, and since forehand slices are so rare, I’ve left those out of today’s discussion as well.

The forehand reigns

The numbers above shouldn’t come as a surprise. The average ATP player has a stronger forehand than backhand, regardless of how many hands are on the racket for the latter shot. Novak Djokovic possesses one of the best backhands in the history of sport, but the gap between his FHP and BSP numbers is greater than average: +11.3 per match for the forehand, and +2.5 for the backhand, resulting in a difference of 8.8. Even a backhand master reaps more rewards on his other side.

The Match Charting Project has at least three matches worth of data for 299 different men across several generations, spanning from Vitas Gerulaitis to Jannik Sinner. Only 30 of them–about one in ten–gain more points on their backhand than on their forehands, and for half of that minority, the difference is less than a single point. It’s a diverse group, including Pat Cash, Jimmy Connors, Guillermo Coria, Ernests Gulbis, Daniil Medvedev, and Benoit Paire. This mixed-bag minority doesn’t provide much evidence to settle the question.

Proponents of the “weaker side” argument often point to the arrival of Lleyton Hewitt as a turning point between the net-play-was-feasible era and the approach-at-your-peril era. Others might point to Andre Agassi. As it turns out, both of these figures are surprisingly average.

The Match Charting Project has extensive records on both men. Hewitt’s forehand was worth +10.0 per match, while his backhand and slice combined for +2.9. That’s a difference of 7.1, a bit greater than average, though less than Djokovic’s. Agassi’s FHP was good for +13.0 per match, compared to a BSP of +6.8. That’s a difference of 6.2, even closer to the mean than Hewitt. Ironically, that gap is almost identical to that of Pete Sampras, whose FHP of +6.3 and BSP of -0.1 were equally spaced, even though his groundstrokes were considerably less effective.

Comparing eras

We can’t answer a general question about trends over time simply by calculating shot potencies for individual players, no matter how pivotal. Instead, we need to look at the whole population.

First, a quick note about our data: The Match Charting Project is extremely heavily weighted toward current players. Our sample of 300 players consists of only 40 whose careers were mostly or entirely in the 20th century, and 30 more whose matches mostly took place in the first decade of this century. Thus, the averages mentioned above are skewed toward the 2010s. That said, the 70 “older” players in the sample are the most prominent–the guys who played in major finals and semi-finals, and Masters finals. If there has been a marked trend across decades, those players should help us reveal it.

The earlier players in our sample are, in fact, quite similar to the contemporary ones. I ranked the 299 players by the absolute difference between their FHP and their BSP, with the most balanced player ranked 1, and the least balanced ranked 299. I looked at two subgroups: the 52 oldest players in the sample, most of whose careers were fading out when Hewitt arrived; and the 78 players with the most recent matches in the sample.

Oldest — Average rank: 143, Average (FHP – BSP): 5.7
Most recent — Average rank: 155, Average (FHP – BSP): 6.5

These numbers do not indicate that players used to have a weak side, and now they don’t. They don’t really reflect any trend at all. The difference between forehand effectiveness and backhand side effectiveness has barely changed over several decades.

As further evidence, here is a selection of players who are both well-represented in the Match Charting Project data and noteworthy representatives of their eras. They’re listed in approximate chronological order. Each of the shot-potency numbers is given on a per-match basis, and the final column (“Diff”) is the difference between FHP and BSP–the gap between each player’s forehand and backhand sides.

Player              FHP    BHP   SLP   BSP  Diff  
Bjorn Borg          12.9  11.5  -0.5  11.0   2.0  
Jimmy Connors       6.5    9.1  -0.3   8.9  -2.4  
John McEnroe        2.0   -0.4  -2.1  -2.4   4.4  
Mats Wilander       7.2    6.8  -0.5   6.3   0.9  
Ivan Lendl          10.3   4.0   0.6   4.6   5.7  
Stefan Edberg       1.9    1.8  -1.1   0.7   1.1  
Boris Becker        5.9    2.1  -1.5   0.7   5.2  
Jim Courier         13.3   4.2  -0.3   3.9   9.4  
Michael Stich       2.0    2.0  -3.4  -1.4   3.4  
Michael Chang       9.7    5.0  -0.6   4.4   5.3  
                                                  
Player              FHP    BHP   SLP   BSP  Diff  
Thomas Muster       18.4   2.2  -1.1   1.1  17.3  
Pete Sampras        6.3    0.7  -0.7  -0.1   6.4  
Andre Agassi        13.0   7.2  -0.5   6.8   6.3  
Patrick Rafter      3.5    0.5  -1.6  -1.1   4.6  
Carlos Moya         9.8   -0.9  -1.4  -2.3  12.1  
Lleyton Hewitt      10.0   3.5  -0.6   2.9   7.1  
Guillermo Coria     4.7    6.3  -1.2   5.2  -0.5  
David Nalbandian    8.8    5.6  -1.7   3.9   4.9  
Nikolay Davydenko   7.2    4.4  -1.2   3.2   4.0  
Roger Federer       10.0   0.2  -0.4  -0.3  10.2  
                                                  
Player              FHP    BHP   SLP   BSP  Diff  
Rafael Nadal        15.3   2.6  -1.0   1.6  13.7  
Andy Murray         7.2    2.9  -1.8   1.1   6.1  
Novak Djokovic      11.3   3.4  -0.8   2.5   8.8  
Richard Gasquet     1.9    1.4  -1.4   0.0   1.9  
Stan Wawrinka       6.2    0.5  -1.7  -1.2   7.3  
Kei Nishikori       5.4    3.8  -1.1   2.7   2.8  
Dominic Thiem       9.3   -0.1  -1.6  -1.7  11.0  
Alexander Zverev    3.6    4.2  -1.1   3.0   0.6  
Stefanos Tsitsipas  8.3   -0.9  -2.2  -3.0  11.4  
Daniil Medvedev     1.6    3.3  -1.4   1.9  -0.3

Not weaker, but weak

These numbers cast a lot of doubt on the “weaker side” hypothesis, that it used to be easier to move forward by approaching an opponent’s less dangerous wing.

Instead, what has probably happened is that for the typical player, both sides got stronger. As a result, the weaker side was no longer flimsy enough to make approaching the net a profitable strategy. Even players with weaker-than-average backhands are now able to hit powerful topspin passing shots. This is essentially the racket-and-string-technology argument, and it seems to me to be the most valid.

There’s no question that tennis has drastically changed in the last few decades. But the conventional explanations for those trends don’t always hold up under scrutiny. In this case, while volleys have been reduced to a vestigial part of the singles game, groundstrokes–on both sides–have only gotten better.

Mackie McDonald’s Secret Weapon

Italian translation at settesei.it

In the first round on Monday, the 23-year-old American Mackenzie McDonald defeated young Russian Andrey Rublev in four sets, 6-4 6-4 2-6 6-4. While Rublev missed part of the 2018 season due to injury and carries a ranking just inside the top 100, the victory still qualifies as a bit of an upset for McDonald, who has never come close to Rublev’s peak of No. 31.

The handful of fans who kept tabs on Court 10 were treated to an unusual display. The American relentlessly attacked Rublev’s second serve, rushing the net behind his return almost two dozen times. Many players don’t hit return approach shots that often in an entire year. What’s more, the tactic worked. Without it, the already close match would have been a coin flip.

By my count, in the log I kept for the Match Charting Project, McDonald came in behind his second serve return 22 times. Approach shot counts are never precise, because when a player hits a winner or an error, he may lean forward as if to continue toward the net, but quickly stop when he realizes it’s unnecessary. To be precise, he came in at least 22 times, and perhaps one more return winner or a couple of return errors should also be added to the total. No matter, the conclusions are similar regardless of whether the number is 22 or 24.

Rublev hit 62 second serves, but 9 of those resulted in double faults, so we’re looking at 53 playable second serves. McDonald netrushed 22 of those, winning 10. Of the other 31, he won only 11. That’s a return winning percentage of 45% on return approaches compared to 35% on other returns. Had he won all of those points at the 35% rate, it would have cost him two, perhaps three points off his overall total. He barely outscored Rublev as it was, 124 points to 118, so every little bit helped.

A rarity in context

The Match Charting Project has shot-by-shot data for nearly 2,000 men’s matches from this decade, and Monday’s four-setter was the first one of those in which a player hit at least 20 second-serve return approaches. (Dustin Brown approached at a higher rate in multiple matches, including his 2015 Wimbledon upset of Rafael Nadal.) There are only ten other matches in the database in which one player hit at least ten such approaches, and Mischa Zverev accounts for three of them. More than three-quarters of the time, the total number of second-serve return approaches is zero.

McDonald is not alone in enjoying some success with the tactic: The 1500 or so second-serve return approaches in the dataset were about 14% more effective than non-approaches in the same matches. However, it’s hard to be sure what that number is telling us, since most players approach so rarely. Some of the attacks are probably on-the-fly decisions against particularly weak serves, not pre-planned plays like many of Mackie’s netrushes on Monday.

Thus, it’s difficult to know how much success most men would have with the tactic, were they to adopt it more often. The fact that they employ it so rarely might tell us all we need to know: If more players thought that attacking the net behind the second serve return would win them more points, they’d do it. But for McDonald, it doesn’t matter what his peers do; it only matters what works for him. These 22 return approaches represented a lot more aggression than he displayed in the four previous matches we’ve charted, and it paid off.

It wasn’t enough to get him a win today against Marin Cilic, but he did outperform expectations, taking a set against the 6th seed and defending finalist. Best of all, he won more than half of Cilic’s second-serve points–a better rate than he managed against Rublev, and several ticks above 46%, the fraction that the average opponent manages against Cilic. In a sport often criticized for its uniformity of tactics, McDonald is an up-and-comer worth watching.

The Right Amount of Serve-and-Volley

Embed from Getty Images

Italian translation at settesei.it

In modern tennis, players approach the net at their own peril, especially behind their serve. Technological advances in both strings and rackets have made passing shots faster and more accurate, giving an added edge to the returner. It’s hard to imagine the game changing so that serve-and-volleying would once again become a dominant tactic.

Yet pundits and commentators often suggest that players should approach the net more often, sometimes advocating for more frequent serve-and-volleying. In a recent article at FiveThirtyEight, Amy Lundy brought some numbers to the discussion, pointing out that at the US Open this year, women have won 76% of their serve-and-volley points and men have won 66%. She also provides year-by-year numbers from the women’s Wimbledon draw showing that for more than a decade, the serve-and-volley success rate has hovered around the mid-sixties.

Sounds good, right? Well… not so fast. Through the quarter-finals in New York, men had won roughly 72% of their first-serve points. Most serve-and-volley attempts come on first serves, so a 66% success rate when charging the net doesn’t make for much of a recommendation. The women’s number of 76% is more encouraging, as the overall first-serve win rate in the women’s draw is about 64%. But as we’ll see, WTA players are usually much less successful.

Net game theory

When evaluating a tactic, we have to start by recognizing that players and coaches generally know what they’re doing. Sure, they make mistakes, and they can fall into suboptimal patterns. But it would be a big surprise to find that they’ve left hundreds of points on the table by ignoring a well-known option. If more frequent serve-and-volleying was such a slam dunk, wouldn’t players be doing so?

I dug into Match Charting Project data to get a better idea of how often players are using the serve-and-volley, how successful it has been. and, just as important, how successful they’ve been when they aren’t using it. The results are considerably more mixed than the serve-and-volley cheerleaders would have it.

Let’s start with the women. In close to 2,000 charted matches from 2010 to the present, I found 429 player-matches with at least one serve-and-volley attempt. After excluding aces, regardless of whether the server was intending to approach, those 429 players combined for 1,191 serve-and-volley attempts–95% of them on first serves–of which they won 747. Had those players not serve-and-volleyed on those 1,191 points and won at the same rate as their first- and second-serve baseline points in the same matches, they would have won 725 points. In other words, serve-and-volleying resulted in a winning percentage of 62.7%, and staying back was good for 60.9%. Just to be clear, this is a direct comparison of success rates for the same players against the same opponents, controlling for the differences between first and second serves.

A difference of nearly two percentage points is nothing to sneeze at, but it’s a far cry from the more than ten percent gap we’ve seen on the women’s side at the US Open this year. And it might not be enough of a benefit for many players to overcome their own discomfort or lack of familiarity with the tactic.

When we apply the same analysis to the men, the results are downright baffling. We have more data to work with here: In nearly 1,500 charted matches from 2010 to the present, more than half of the possible player-matches (1,631) tried at least one serve-and-volley. About four in five–once again excluding aces–were first serves. The tour-wide success rate was similar to what we’ve seen at the Open this year, at 66.8%.

Controlling for first and second serves, the same servers, at the same tournaments, facing the same opponents, won points at a 72.2% rate when they weren’t serve-and-volleying. That’s a five percentage point gap* that says men, on average, and serve-and-volleying too much.

* Technical note: These overall rates simply tally all the serve-and-volley attempts and successes for all players. Thus, they may give too much weight to frequent netrushers. I ran the same calculation in two other ways: giving equal weight to each player-match, and weighting each player-match by ln(a+1), where a is the number of serve-and-volley attempts. In both cases the gap shrunk a bit, to four percentage points, which doesn’t change the conclusion.

I was shocked to see this result, and I’m not sure what to make of it. It’s roughly the same for men who serve-and-volley frequently as for those who don’t, so it isn’t just an artifact of, say, the odd points that an Ivo Karlovic or Dustin Brown plays from baseline, or the low-leverage status of the occasional point when a baseliner decides to serve-and-volley. Since I don’t have a good explanation for this, I’m going to settle for a much weaker claim that I can make with more confidence: The evidence doesn’t suggest that men, in general, should serve-and-volley more.

Data from the women’s game is more encouraging for those who would like to see more serve-and-volleying, but it is still rather modest. Certainly, the 76% success rate in Flushing this year is a misleading indicator of what WTA players can expect to reap from the tactic on a regular basis. It’s possible that some women should come in behind their serves more often. But the overall evidence from a couple thousand matches suggests sticking to the baseline is just as good of a bet–if not better.

Should WTA Players Approach the Net More?

Italian translation at settesei.it

21st-century women’s tennis is a baseline game. Some players are better able to identify opportunities to approach the net than others, and some can handle themselves quite well when they get there. But if a fan from a few decades ago were dropped off at the 2014 Australian Open, she would be shocked by the rarity of net points and the clumsiness of many players when they move forward.

Since almost all television commentators were excellent players in a more net-centric era, a frequent refrain during almost any broadcast is that players should rush the net more often. “Frequent” might be understating it–in a fit of pique, I was driven to say this:

Drinking game: Take a drink every time the comm says a player should come to the net more.

Warning: You will die.

— Jeff Sackmann (@tennisabstract) January 13, 2014

Regardless of repetition, it’s worth further investigation. It’s certainly true that a skilled netwoman could win more points by moving forward. But when pros don’t emphasize that part of their game and they gain little match experience approaching the net, do they have the skills necessary to take advantage of such an opportunity?

Enter some numbers

At this point, you might be tempted to look at the oft-collected “Net Points” stat. Resist the urge. In a baseline-oriented match, net points can have little to do with net approaches. Attempting to return a drop shot is considered a net point. Putting away a weak service return is considered a net point. In many WTA matches, more than half of “net points” do not involve an approach. The player was induced to come to the net for some reason.

Making matters worse, that non-approach segment of net points has little to do with net approaches. Given a weak, floating return, any competent player should be able to whack it for a swinging volley winner. At the other end of the spectrum, chasing down a drop shot relies on a different set of skills than picking a moment to hit an approach shot and then confidently placing a volley or two.

Fortunately, the Match Charting Project gives us some more detailed, approach-specific data.

Twenty matches in the charting database are from the first month of the 2014 WTA season, most of them from the first week in Melbourne. This data differentiates between “net approaches” and “net points.” In one of the more aggressive performances in the database, Angelique Kerber, in her loss to Tsvetana Pironkova in Sydney, won 15 of 19 net points. Of her ten net approaches, she won all ten.

(For any match report in the charting database–here’s the Kerber-Pironkova match–click one of the two “Net Points” links to see those stats. There is a different table for each player.)

Kerber’s ten net approaches is tied for the most of any of the WTA matches that have been charted this year. Last night, Garbine Muguruza also tallied ten net approaches, though she did so in a longer match.

In these twenty matches, only 27 of 40 players made even one traditional net approach. Including those who made zero, the average is just over three net approaches per match. The 27 who approached the net at least once averaged 4.7 per match.

Clearly, a lot of opportunities for offense are going unclaimed.

How they’re doing

Of the 126 net approaches we’ve tracked, the approaching player has won 84–exactly two-thirds. While that isn’t an overwhelming endorsement–many approach shots are hit in response to a weak groundstroke that already puts the opponent at a disadvantage–it certainly doesn’t count as evidence against the practice.

In half of all net approaches, the netrusher either hits an outright winner at the net or induces a forced error with a net shot. Only 12% of the time does the opponent hit a passing shot winner. In another 5% of these points, the opponent induces a forced error with a passing shot. In 12% of net approach points, the player who moved forward hits an unforced error at the net.

Of the 27 players in the database who approached the net at least once, only six failed to win half of those points (three of whom only came forward once), and three more won exactly half of their net approach points.

The women in this sample who seize the most opportunities to rush the net have been particularly successful, as well. Seven of the eight who moved forward the most won more than half of their approach points. This allows us to tentatively conclude that all the other players–the ones who picked only a few spots to approach the net during their matches–could have seized more opportunities. There may be a limit in the modern game to how much netrushing is wise, but the observed maximum of ten points per match doesn’t seem to be it.

Inevitable unknowns

Whether we look at Kerber and her 10/10 net-approach performance in Sydney or Sloane Stephens and her 1/1 tally yesterday against Elina Svitolina, it’s impossible to know the results of the next approach shot–or the next five. We can compare single-match results and see that it’s possible for a WTA player to have a perfect record on her ten net approaches, but we can’t perform lab experiments in which Sloane plays Svitolina again and comes forward ten times instead of one.

For all the success that players enjoy when they do move forward, there are plenty of reasons not to. As I said at the outset, today’s players don’t practice net skills nearly as much as baseline skills, and they certainly don’t get much in-match practice. If someone isn’t comfortable approaching the net at a certain time, is it really a good idea for her to do so?

In the abstract, both intuition and statistical analysis supports the position that WTA players could move forward more. When they do approach the net, they are often successful, putting away volley winners and rarely getting passed. But I suspect this implies a long-term strategy more than the sort of thing a coach should emphasize during a changeover.

When commentators suggest that a player should move forward, what I think they really mean is this: “If this player were more comfortable with her transition game, this would be a great opportunity to take advantage of that.” Or: “Players should work harder on their approach shots on the practice court so that they’re ready for opportunities like this one.” Or simply: “Martina would have won that point ten shots ago.”

There seems to be opportunity waiting for more, well, opportunistic young players. But it isn’t one that can be generated simply by a sudden coaching change or a harangue from John McEnroe. Only when a player emerges with the baseline game to contend with the best pros and a transition/net game that exceeds most of those on the tour today will we find out just how much opportunity today’s players have wasted.