Italian translation at settesei.it
In the second-set tiebreak of Sunday’s Cincinnati final, Simona Halep reached match point against Kiki Bertens. She failed to convert, then Bertens claimed the tiebreak, and the third set–and the championship–went the way of the Dutchwoman. It was a bit of painful deja vu for Halep fans, who watched the top-ranked player reach match point against Su Wei Hsieh at Wimbledon only to miss her chance and crash out in the third round.
Halep has a reputation as a bit of a weak closer–not just match points, but set points and, more generally, service games with the set or match on the line. Her overall ability to finish matches is beyond the scope of a single post, but we can start by biting off the smaller chunk of, specifically, her performance on match points, and how that compares to the rest of the WTA.
Let’s start with the basics. For everyone, reaching match point is (obviously!) a really good sign that she’ll go on to win the match. Across about 16,000 WTA matches since 2011 for which I have sequential point-by-point data, players who hold match point end up winning the match a bit more than 97% of the time. That doesn’t mean that they convert on the first try, or even in the game or set of their first opportunity, but even when conversion is elusive, players manage to generate more chances until they finish the job.
If Simona really is a weak closer, we’ll need to look elsewhere for evidence. In the matches for which I possess the point-by-point sequence*, there are 251 contests in which Halep held a match point, stretching between the end of 2011 and this month’s Rogers Cup in Montreal. Of those, she eventually converted a match point 250 times. That is, with the exception of the Wimbledon match against Hsieh, she didn’t lose any matches in which she was a point away from victory.
* I don’t have the point-by-point sequence for every Halep match, but I have most of them, and the missing ones are random. The same applies to just about every WTA player. Some of the raw data is available here; I’m hoping to update with 2017 and 2018 data in the near future.
Compared to the best players, this level of MP conversion doesn’t even stand out. Among the 50 women with at least 100 matches in which they held match point, five–Serena Williams, Victoria Azarenka, Andrea Petkovic, Ekaterina Makarova, and Elena Vesnina—always converted, if not always on the first try. (Again, I’m missing some matches, but that doesn’t take away from the fact that in a random sample of 259 matches, Serena remains perfect.) Until Sunday’s Cincinnati final, Halep was one of eight more–with Petra Kvitova, Maria Sharapova, and Ana Ivanovic, among others–who failed to convert only once.
Situational performance
It’s no accident that the most dominating names in tennis are near the top of that list. Yes, the best players are most likely to win at match point, but just as important, the best players are more likely to earn several opportunities. Deep in a tiebreak, one missed chance can represent the final hope, but most of the time when Halep, Serena, or someone else of their ilk fails to convert an opportunity, they’re still leading by, say, a set and a break, making it easy to generate more chances.
That leads us to another question: How do players perform on match point itself? Does the pressure lead to fewer points won, compared to non-MP serve and return points? Or do other factors, like momentum or crowd support, cause players to do even better when one point away from victory?
It turns out that there’s no single answer; the results are a bit different depending on whether the player holding match point is serving or returning. When a player is serving to finish off a match, she is slightly less likely to win the point, compared to her serve performance up to that point. It’s not a big difference–a bit less than a 3% drop in the rate of serve points won–but it is persistent across several years of WTA results. When players are one point away from victory but are returning, there is no match-point effect. They win return points at the same rate regardless of whether a handshake is imminent.
Match points are almost evenly distributed between serve and return points–on the WTA tour, about 55% are serve points, leaving 45% return points. Thus, given the 3% drop on serve performance and the lack of change on return points, players win approximately 1.5% fewer points when one step away from victory than otherwise. One player who almost exactly parallels the average is Caroline Wozniacki–in 271 match-point matches and 474 match points, she won those MPs at a rate 1.7% lower than non-MPs.
Some of the players who almost always win their match-point matches aren’t any better than average when we look at individual points. For instance, Sharapova wins MPs a rate 1.2% lower than non-MPs, and Azarenka’s success rate drops by 1.4%. Dominika Cibulkova won 198 of the 201 match-point matches in my dataset despite her success rate falling by a whopping seven percent.
Halep, however, doesn’t fit in that category. In her 251 match-point matches, she has held 420 individual match points, which she has won at a rate 4.4% higher than her non-MP rates in the same set of matches. Few players are better, though a handful are overwhelmingly so, such as Kvitova at +9.0%, and Vesnina at +13.9%. The vast majority of women are within a few percentage points of neutral: They win match points, whether serve or return, about as often as they win non-match-points.
Random results
These numbers tell us only one thing: what has happened in the past. It is tempting to use them to make predictions, or perhaps lay down a sizable wager the next time Vesnina is a point away from victory. But when most players are so close to neutral, it’s a warning that much of what we’re looking at may be random.
If players have consistent tendencies in match point situations, we would be able to identify that in the data. For instance, we might see that Kvitova converts match points at a high rate in each individual season. Since the single-season totals make for sometimes small samples, I took a slightly different approach. For players with at least 60 match-point matches, I randomly divided their matches into two separate groups, and determined how their performance at MP compared to their success rate on other points. Again, if this were a real skill, we would expect that players would be roughly the same in each of their two random groups–better than usual on MP in both groups, or worse.
Alas, for this population of 80 players with sufficient match-point samples, there is no correlation at all. If women have consistent, predictable tendencies to outperform or underperform in match-point opportunities, these inclinations are either extremely small, or they don’t persist over several years.
This is a familiar refrain when looking at specific situations in tennis matches. Our hyperactive, pattern-seeking brains find it easy to identify apparent tendencies, but in general, players win points at about the same rate regardless of the context. Over the medium term, like the half-decade represented by my point-by-point dataset, some players will stick out, like Kvitova, Vesnina, and to a lesser extent, Halep. But past results are hardly a guarantee of future match-point performance. The smart prediction for any player’s upcoming results on match point is that she’ll do exactly as well as she does the rest of the time. It’s a rather boring conclusion. Thankfully, the match points situations themselves are usually exciting enough on their own.