Is Serena Williams Taking Advantage of a Weak Era?

tl;dr: No.

Serena Williams is, without question, the best player in women’s tennis right now. She’s held that position off and on for over a decade, and it’s easy to make the case that she’s the best player in WTA history.

The longer one player dominates a sport, the tougher it is to distinguish between her ability level and the competitiveness of the field. Is Serena so successful right now because she is playing better than any woman in tennis history, or because by historical standards, the rest of the pack just isn’t very good?

As we’ll see, the level of play in women’s tennis has remained relatively steady over the last several decades. While there is no top player on tour these days who consistently challenges Serena as Justine Henin or peak Venus did, the overall quality of the pack is not much different than it has been at any point in the last 35 years.

Quantifying eras

Every year, a few new players break in, and a few players fade away. If the players who arrive are better than those who leave, the level of competition gets a bit harder for the players who were on tour for both seasons. That basic principle is enough to give us a rough estimate of “era strength.”

With this method, we can compare only adjacent years. But if we know that this year’s field is 1% stronger than last year’s, and last year’s field was 1% stronger than the year before that, we can calculate a comparison between this year’s field and that of two years ago.

Since 1978, the level of play has fluctuated within a range of about 10%. The 50th-best player from a strong year–1995, 1997, and 2006 stand out–would win 7% or 8% more points than the 50th-best player from a weak year, like 1982, 1991, and 2005. That’s not a huge difference. One or two key players retiring, breaking on to the scene, or missing substantial time due to injury can affect the overall level of play by a few percentage points.

The key here is that a dominant season in the mid-1980s isn’t much better or worse than a dominant season now. Perhaps Martina Navratilova faced a stiffer challenge from Chris Evert than Serena does from Maria Sharapova or Simona Halep, but that difference is at least partially balanced by a stronger pack beyond the top few players. Serena probably has to work harder to get through the early rounds of a Grand Slam than Martina did.

Direct comparisons

So, Serena’s great, and her greatness isn’t a mirage built on a weak era. Using this approach, how does she compare with the greats of the past?

Given an estimate of each season’s “pack strength,” we can rate every player-season back to 1978. For instance, if we approximate Serena’s points won in 2015 (based on games won and lost), we get a Dominance Ratio (the ratio of return points won to serve points lost) of 2.15. In layman’s terms, that means that she’s beating the 50th-ranked player in the world by a score of 6-1 6-1 or 6-1 6-2. The 2.15 number means she’s winning 115% more return points than that mid-pack opponent. If the pack were particularly strong this season, we’d adjust that number upwards to account for the level of competition.

Repeat the process for every top player, and we find some interesting things.

Serena’s 2.15–the second-best of her career, behind 2.19 in 2012–is extremely good, but only the 21st-ranked season since 1978. By this metric, the best season ever was Steffi Graf‘s 1995 campaign, at 2.42, with Navratilova’s 1986 and Evert’s 1981 close behind at 2.38.

Graf has seven of the top 20 seasons since 1978, Navratilova has four, and Evert has three. Venus’s 2000 ranks sixth, while Henin’s 2007 ranks tenth.

It seems to have become harder to post these extremely high single-season numbers. In the last ten years, only Serena, Henin, Sharapova, Kim Clijsters, and Lindsay Davenport have posted a season above 2.0. Serena has done so four times, making her the only player in that group to accomplish the feat more than once.

Best ever?

As we’ve seen in comparing Serena’s best seasons to those of the other greatest players in WTA history, it’s far from clear that Serena is the greatest of all time. Graf and Navratilova set an incredibly high standard, and since the greats all excelled in slightly different ways, against different peer groups, picking a GOAT may always be a matter of personal taste.

Assigning a rating to the current era, however, isn’t something we need to leave up to personal taste. I’m confident in the conclusion that Serena is not simply padding her career totals against a weak era. If anything, her own dominance–during an era when dominating the women’s game seems to be getting harder–is making her peers look weaker than they are.

Ivo Karlovic and His Remarkable 10,466* Aces

Here’s the official story: This week, Ivo Karlovic crossed the much-heralded 10,000-ace milestone. Next up is the all-time record of 10,183 aces, held by Goran Ivanisevic.

Karlovic is one of the greatest servers in the game’s history, and he has in fact hit more than 10,000 aces. Ivanisevic was really good at serving, too, and he might even hold the all-time record. But when it comes down to the details in this week’s ATP press releases, all the numbers are wrong.

Last year, Carl Bialik laid out the two main problems with ATP ace records:

  • The ATP doesn’t have any stats from before 1991. (Ivanisevic started playing tour-level matches in 1988.)
  • ATP totals don’t include aces from Davis Cup matches, even though Davis Cup results are counted toward won-loss records and rankings.

I’ll add one more: There are plenty of other matches since 1991 with no recorded ace counts, too. By my count, we don’t have stats for 14 of Ivanisevic’s post-1991 matches. (They’re not on the official ATP site, anyway.) That doesn’t count Davis Cup, the Olympics (also no stats), and the now-defunct Grand Slam Cup.

If you like tracking records and comparing the best players from different eras, tennis might not be your sport. All of these problems exist for players who retired only recently, and some of the issues persist to the present day. And if you want to compare Federer or Ivanisevic with, say, Boris Becker or–it’s tough to write this without laughing–Pancho Gonzalez, you’re completely out of luck.

We’ll probably never find ace totals from all of the missing matches. But it seems silly to pretend we can identify the true record-holder and celebrate when these “records” are broken when we so obviously cannot.

Approximate* career* totals*

What we can do is estimate the number of missing aces for each of the top contenders. In Ivanisevic’s case, his 1988-90 seasons, combined with Davis Cup and other gaps in the record, total nearly 200 matches. Even if we can’t pinpoint the exact number of uncounted aces, we can come up with a number that demonstrates just how far ahead of Karlovic he currently stands.

To fill in the gaps, I calculated each player’s rate of aces per game for each surface for every season he played. For 1988-90, I used 1991 rates. (This post at First Ball In, which I discovered after writing mine, suggests that players improve their ace rates the first few seasons of their careers, so we should adjust a bit downward. That may be right. A 5% penalty for Goran’s 1988-90 knocks off about 60 aces from his total below.)

Once we crunch the numbers, we get an estimated 2,368 aces in Ivanisevic’s 195 “missing” matches. That gives him a career total of 12,551–a mark Karlovic couldn’t achieve until the end of 2017, if then.

But wait–Ivo has some missing matches, too! The gaps in his record only amount to 21 matches, mostly Davis Cup. The same approximation method adds 466 aces to his record, meaning he hit that 10,000th ace back in June, in his second-rounder against Alexander Zverev. Even with those nearly 500 “extra” aces, Ivanisevic’s record is almost surely out of reach.

What about Pete Sampras? Officially, Pete is fifth on the all-time list, with 8,858 aces. But like Goran, he played a lot of matches before record-keeping began in 1991. His ace record is missing nearly 200 matches, as well.

In Sampras’s case, we can estimate that he hit 1,815 aces that aren’t reflected in his official total. (In line with the caveat regarding Goran’s total above, we might want to knock that total down by 50 to reflect the possibility that he hit more aces in 1991 than in 1988-90.)

Making similar minor adjustments to the other members of the top five, Federer and Andy Roddick, here’s what the all-time list should look like, at least in general terms:

Player      Official  Est Missing  Est Total  
Ivanisevic     10183         2368      12551
Sampras         8858         1815      10673  
Karlovic       10022          466      10488  
Federer         9279          524       9803  
Roddick         9074          694       9768  

Coincidentally, Karlovic is officially within 200 aces of  Ivanisevic’s all-time record, and while he really isn’t anywhere near the record, he is that close our estimate of Sampras’s second-place total.

We can be confident that Ivo is a great server. But if we can’t be sure of his own ace total, mostly amassed in the last decade, it seems foolish to pretend that we’ll know when–or even if–he breaks the all-time record.

Kei Nishikori’s Unbeatable Run in Deciding Sets

When Kei Nishikori defeated Roberto Bautista Agut in last week’s Barcelona quarterfinals, it was the seventh time in a row that he won a deciding set. By Nishikori’s standards, that’s nothing special. It is the fifth time in his career he’s put together a string of at least seven straight deciding-set wins, three of which he’s recorded since the beginning of last season.

The wider the perspective, the more impressive Kei’s deciding-set record. Since last year’s Australian Open, he’s won 27 of 30 matches that went the distance, including a 13-match winning streak from Halle to London. Back in 2011-12, he won 16 deciding sets in a row, including four against top-ten players.

In his career on tour, Nishikori has won 75 deciding-set matches and lost 20, for a winning percentage of 79%. Using any reasonable minimum number of matches, no other player has come close to that mark. You might recognize some of the other names on this list, ranked by record in deciding sets (minimum 80 matches):

Kei Nishikori   78.9%  
Bjorn Borg      74.7%  
Novak Djokovic  74.1%  
Jimmy Connors   69.8%  
Rafael Nadal    69.5%  
Andy Murray     69.4%  
Rod Laver       68.4%  
John McEnroe    68.1%  
Pete Sampras    68.0%

Kei’s career accomplishments don’t quite stack up with those of this crowd, but in terms of deciding-set performance, we’re looking at much more than an early-career fluke. While his numbers are a bit padded by matches that shouldn’t have gone the distance (like his early-round hiccups in Memphis this year against Ryan Harrison and Austin Krajicek), he has been almost as good when facing the best players in the game. Against top-ten opponents, he’s 17-6, good for a 74% winning percentage–a mark that would still put him near the top of the list.

Let’s return to Nishikori’s outrageous recent record of 27-3 in his last 30 deciding sets. Sure enough, no one has ever done better. Nine other players  have posted an equal mark in a span of 30 deciding-set matches, including Novak Djokovic, Rafael Nadal, Roger Federer, and Nishikori’s coach Michael Chang. Amazingly, Kei himself had already gone 27-3, back in 2011-12.

To break the tie among these accomplishments, we might look at the difficulty of the 30-match span, as measured by deciding sets against top-tenners. When Djokovic went 27-3, between 2011 Dubai and 2012 Canada, he played 15 of those matches against top-ten opponents,winning 14 of them. (Novak is also 27 of his last 30, including 15 of 17 against top-tenners.) When Nadal had his run, between 2008 Dubai and 2009 Paris, he faced 12 top-tenners, beating 10. Kei has faced only six, winning five.

It’s clear that Nishikori’s deciding-set prowess is a skill, not just a statistical fluke built on easy draws and luck. And based on the performance of the other players who have put together equally impressive deciding-set streaks, we can expect Kei to win most of his upcoming three- and five-setters.

Including streaks that overlap, there have been 27 instances in ATP history when a player won 27 of 30 deciding-set matches, excluding Kei’s and Novak’s current spans. In the ten deciding-set matches that followed each of those streaks, in each instance the player won at least five, and the average was just under seven.

Only once in ATP history has a player gone 27-3 in deciding-set matches and followed it up by winning nine of his next ten. If Nishikori is to match or better that mark, at least he’s assembled the right team: The player he’s chasing is Michael Chang.

Novak Djokovic and the Best Fifty-Match Stretches

Few players have ever been as dominant as Novak Djokovic is right now. Over his last fifty matches, he has posted stats that are almost too good to be believed:

Armed with stats going back 25 years, we can see how Djokovic’s current performance compares with the best in recent ATP history. In some categories, he is indeed atop the list. In others, he’s merely very close to the best ever.

Let’s start with the simple matter of won-loss record. 47 wins in 50 matches is excellent by any standard. Only four players–Roger Federer, Rafael Nadal, Thomas Muster, and Djokovic himself–have done better. Pete Sampras also won 47 of 50 in a stretch in 1993-94.

The category in which Djokovic most clearly stands out is his performance against top-10 opponents. His 21 top-10 wins in a 50-match stretch outpaces the best of Nadal (18, in 2013), Federer (17, in 2006-07), and Andre Agassi (17, in 1994-95). Only 12 different players have won ten top-10 matchups in a 50-match stretch, let alone 20. Novak’s 23 top-10 matches is also the highest on record.

Then there are the bagels. In this span, Djokovic has won 13 sets by a 6-0 score. That’s not quite the best: Federer won 14 in his 2006-07 stretch. Sergi Bruguera (1993) and Agassi (1992-93) also show up here, with 13 bagels over the course of 50 matches.

Finally, let’s turn to aggregate statistics. Dominance Ratio (DR) is the ratio of return points won to serve points lost, and serves as a simple yardstick for–you guessed it–dominance. A DR of 1.0 indicates the two players were equal, 1.1 is a narrow win, and anything in the 1.5 range is a comfortable victory.

As Carl noted in that tweet, Djokovic has maintained a DR of nearly 1.5 over his last 50 matches. That’s not the best of all time–in fact, it’s not even Novak’s best. From 2013 Cincinnati to the second round of 2014 Monte Carlo, Djokovic posted a cumulative DR of 1.49, just edging out his current streak.

But neither mark is number one on the list. As with so many other categories, this one belongs to 2006 Federer. From the 2006 Halle final through the end of the 2007 Australian Open, Fed won 49 of 50 matches, 16 of 16 matches against the top 10, served 14 bagels, and posted an overall DR of 1.54. It would take an extremely strong performance from Djokovic over the next few weeks–even by his own standards–to reach those heights.

If you prefer the more traditional metric of total points won, Fed is still your number one, at 56.84% over that 2006-07 span. A different streak of Novak’s–his historic 2011 run–comes in a very, very close second, at 56.77%. Nadal put together a stretch in 2012-13 of 56.6%. The entire top ten is dominated by these three guys; the only other player who has won more than 56% of total points over 50 matches is Guillermo Coria, who did so in 2003.

Comparing Novak’s current streak to the rest of the field merely emphasizes how much distance he has placed between himself and the pack. Federer’s DR over his last 50 matches is a very respectable 1.37, with Nadal not far behind at 1.29. Kei Nishikori and Milos Raonic aren’t far behind in the official rankings, but by this measure they have an immense amount of ground to make up, with cumulative DRs of 1.17 and 1.16, respectively.

For Djokovic right now, a number that starts with 1.1 is a bad day. In his last 50 matches, he has sunk below 1.2 only seven times. Whichever metric you prefer, we’re watching one of the great performances of modern tennis history.

Dominic Thiem’s Qualifying Marathon

When Dominic Thiem beat Marinko Matosevic in Madrid qualifying this week, it was the seventh time this year he fought his way into a tour-level main draw.  Seven is an awful lot for one season–and it’s early May. Last season, Santiago Giraldo qualified more than any other player, doing so only six times.

In fact, Thiem could easily set the all-time record. Only 46 players have ever qualified for seven or more tour-level events in a season, and 29 of those have stopped at seven. 10 players have qualified eight times, including Flavio Cipolla in 2011, Teymuraz Gabashvili in 2007, and Alejandro Falla in 2007 and 2009. An even smaller group of seven players have reached nine main draws through qualifying, most recently Kevin Anderson in 2010.

No one has ever reached double digits, and Thiem has almost six months in which to close the gap.

Perhaps the most impressive thing about Thiem’s run is that he has failed to qualify only once this year, in Acapulco. At most ATP events, qualifying requires winning two matches, and twice this year he’s needed to win three. It’s a level of consistency almost unheard of among young players, or players of any age at his level in the rankings. It’s comparable to reaching the quarterfinals or better at seven of eight consecutive particularly strong Challengers.

If the Austrian fails to set a new record, it probably won’t be because he’s not good enough–it’s more likely to end up that way because he’s too good. His ranking started the year at #139, and after his win over Stanislas Wawrinka yesterday, he’ll ascend to almost #60 next Monday. That isn’t good enough to make the main draw cut at most Masters 1000 events, but it will earn him direct entry into anything else.

Thiem has climbed so high not just because of his success in qualifying, but also because of his performance after qualifying. In six of the seven main draws he has reached the hard way, he won at least one match, including three against seeded players. That sets him apart from other recent qualifying warriors. For instance, in 2009 Falla qualified for eight main draws and won only two matches. In 2010 Anderson won five main draw matches in nine main draws as a qualifier.

While qualifying records are impressive and entertaining, it is Thiem’s consistency and his quality play in main draws that bode well for his future as a top player on tour. Guys like Cipolla and Falla have qualified so much because they manage to stick around in a certain tier of the rankings without ever advancing any higher, not because they were ever on the brink of stardom.

That’s why, if Thiem does qualify for ten main draws this year, it will likely be the last qualifying-related record he sets. Falla leads active players with 37 successful trips through qualifying in his career, and that’s a mark the Austrian will never threaten.

Statistical Quirks in Munich and Oeiras

From Monday to Sunday last week, the ATP 250s in Munich and Oeiras were filled with statistical quirks.  Here’s a rundown of some of the oddities you might have missed:

  • In both events, the top four seeds in qualifying advanced to the main draw. Since the beginning of the decade, there have been 173 ATP 250s, and these two events were only the 7th and 8th of those in which the four qualifiers were the top four seeds.
  • Not only that, but the four players those qualifiers defeated were the 5th through 8th seeds. Put another way, the eight players in the qualifying round were the top eight seeds.  That hadn’t happened in the 2010s–and it happened in two different tournaments last week.   Of the previous 171 events, seven seeds reached the qualifying round on four occasions, but never eight.
  • In Munich, Tommy Haas won his first two matches as a 36 year old. He wasn’t the first man that old to win a match this year–Marc Gicquel beat him to it in Montpelier–but he’s only the 12th player to do so since 2000.  Still, he has a long way to go to catch Ken Rosewall, who won over 350 tour-level matches after his 36th birthday.
  • In four matches, Fabio Fognini reached the Munich final, but he didn’t play a single direct entrant. After a first round bye, he faced Dustin Brown, a wild card, followed by three qualifiers, Thomaz Bellucci, Jan Lennard Struff, and Martin Klizan. In ATP history, no one has ever played every round of an event without facing another direct entrant.  There have been a few instances when a player faces four non-direct entrants (notably Richard Gasquet‘s 2007 Wimbledon run).  I also found a couple of WTA $10Ks in which a player faced five non-direct entrants, but there are eight qualifying and four wild card spots at that level.
  • Fognini lost to Klizan in the final, a repeat of the final result in 2012 in St. Petersburg. Klizan’s two titles both came against Fognini, making him only the fifth player in ATP history to win his only two finals against the same player.  The Slovak is in good company: The most recent guy on the list is David Ferrer, and before that was Carlos Moya.
  • Back in Portugal, the heavy favorite Tomas Berdych won the first set over Carlos Berlocq by the score of 6-0. That’s rare enough in a tour-level final. Berlocq made it much more unusual, though, when he came back to win.  It was only the 10th time in ATP history that a player won a final after dropping the first set 0-6. The last occurrence was quite recent, when Marcel Granollers came back to win in the Kitzbuhel final last year.
  • Berlocq is known as a fighter, but he had never come back from a 0-6 hole in a tour-level match before. He had done so only once as a pro, in a Challenger match against Marcos Daniel in 2004.
  • Berdych’s record was even more pure, having never lost a professional match after winning the first set 6-0.

One more quirk from the week: By winning the Tallahassee Challenger, Robby Ginepri ended an 11-year-long title drought at that level.  (Though he did win several ATP titles in that time.)  Amazingly, that isn’t a record.  Thomas Johansson went 12 years and two months between Challenger titles, and Tommy Robredo, who ended his own nearly 12-year drought when he won Caltanissetta in 2012.

The Madrid Masters has star power, but this year it’s unlikely to produce as many historical oddities as the week it follows.

Surprise Semifinalists at the Australian Open

Of the eight singles semifinalists in Melbourne, only two entered the tournament seeded in the top four. Rafael Nadal, the top seed in the men’s draw, has survived, and Li Na, the fourth seed in the women’s draw, is the highest-ranked player still alive on her side.

We haven’t exactly followed the script.

The women’s singles draw, with the top three seeds eliminated, is particularly unusual. It is only the 10th time in the last 35 years that none of the top three seeds have made it through to the final four of a Grand Slam. Such events have been heavily concentrated in the last decade or so–the fourth seed was the highest-ranked surviving player at Wimbledon in 2011 (Victoria Azarenka) and 2013 (Agnieszka Radwanska), and the fifth seed was the apparent favorite at Roland Garros in 2011 (Francesca Schiavone).

You might notice a pattern. In these nine Slams when no top-three seed reached the semifinal stage, the best remaining player didn’t fare so well. Both Vika and Aga fell to lower-ranked opponents when they were the remaining favorites at Wimbledon, and Schiavone lost her shot at the French Open to Li. Only twice in these nine majors did the highest-remaining seed in the semifinals go on to win: Martina Hingis, when she was seed fourth at the 1997 Australian Open, and Anastasia Myskina, when she was the sixth seed at the 2004 French Open.

In a tournament full of surprises, we might not be done yet. It stands to reason that once the favorites are eliminated, the odds of subsequent upsets increase. The lower you go in the rankings, the less difference there usually is between players–there’s a bigger gap between Azarenka and Maria Sharapova than there is between, say, Jelena Jankovic and Angelique Kerber. The smaller the gap, the more likely the upset.

While only one top-four seed remains in the men’s draw, the odds of upsets are moving in the opposite direction. While Nadal can always count on a tough fight from second-seed Novak Djokovic, he typically has little trouble with lower-ranked players. He has won his last 15 matches against the other three players left in the drawRoger Federer, Tomas Berdych, and Stanislas Wawrinka–and lost only 4 of 41 matches against the trio since 2008.

The historical precedent for this sort of semifinal draw also favors Rafa. 14 Grand Slams in the Open Era have featured a semifinal round in which the top seed is the only one remaining of the top four. The top seed has gone on to win 9 of the 14, including 8 of the last 10. The most recent final four that fit this profile was in Melbourne four years ago, when Federer swept the final two rounds without losing a set.

But even this rosy picture for Nadal offers Roger a glimmer of hope.  The last time the top seed was alone in the final four and didn’t go on to win was the 2002 US Open. Lleyton Hewitt was the #1 who failed, paving the way for a 31-year-old Pete Sampras to win one final slam before he retired.

Roger isn’t going to call it quits this week, but he’d sure like to emulate Pete’s success in seizing a wide-open Grand Slam draw.