Earlier this week I wrote about Garbine Muguruza’s outstanding start to the season, and I introduced a new method to quantify a player’s level in a relatively short time span. Instead of using traditional Elo, which takes into account everything we know about a player, my new metric, yElo, uses what we know about everyone else, but treats a player’s short-term performance as if it is all we know about her. The parameters for yElo, such as k-value, are the same as the ones I’ve arrived at to make “regular Elo” as predictive as possible.
In other words, we measure Muguruza’s 22 matches in 2021 as if she had never played a WTA event before. As we saw in my earlier post, this approach considers the strength of opponents each player faced, and it rates her 18-4 record as better than anyone else in 2021, including Naomi Osaka’s 10-0 start.*
* excluding walkovers, which I ignore for all versions of Elo and yElo.
Muguruza’s season start has been outstanding and it is definitely underrated by the official WTA rankings and maybe even by the race, but I don’t want to make too much of it–one title in five tournaments in hardly world-historical stuff. On the other hand, it’s a good way to get our feet wet with a new metric that I think will prove useful for a wide range of tennis comparisons.
Garbine vs Garbine
The Spaniard won majors in 2016 and 2017, and she briefly reached number one in the rankings in September of 2017. Those achievements belong on a Hall of Fame plaque over her recent Dubai title and Yarra River Classic final. But was she really playing better back then?
She was not! I ran the yElo formula for every 22-match sequence in Muguruza’s career. The best of the bunch–again, taken entirely out of context, as if we know nothing beyond those 22 matches–was a run late in 2015 when she reached the Wuhan final, won Beijing, then went undefeated in the WTA Finals round robin stage. Her yElo based on those 22 matches was 2172, narrowly better than her 2021 yElo of 2160.
The more memorable moments of her career don’t quite stack up:
Elo W-L Span
2172 17-5 2015 Wim R16 - WTA Finals RR
2160 18-4 2021 Abu Dhabi R64 - Dubai F
2148 18-4 2017 Birmingham R32 - Cinci F
2122 19-3 2017 Wimb R128 - USO R16 (#1)
2084 17-5 2017 Miami R64 - Wimb F
2076 16-6 2016 Doha QF - Roland Garros F
I haven’t shown every 22-match sequence of her career, because that list is long and boring–the streaks heavily overlap with each other, and thus there are often tiny differences between them. But it is instructive to look at the time periods that ended at key moments.
The best of that bunch was the 22-match run ending with Muguruza’s 6-1 6-0 beatdown of Simona Halep at the 2017 Cincinnati final. That set the stage for her ascent to #1, though the ranking move didn’t happen until after the US Open. That streak is close to her current level. The 22 matches leading up to the official #1 takeover are a bit lower (she lost to Petra Kvitova at the US Open, which was less forgivable then than now), and the timespans ending with her two slam finals are still further down the list.
Don’t misunderstand–Muguruza was playing very well throughout all of these time periods. But when we crunch the numbers, we find that her current level is roughly on par with the best she’s ever played.
Garbine vs the world
Metrics are a lot more informative once we gain some context. Many of you probably have a good sense of what regular Elo ratings mean–2100+ is outstanding, 2000+ is top ten-ish, 1900+ is approximately the top 20, and so on. We can piggyback on that for yElo. When Muguruza’s 22-match yElo this season is 2160, it really does mean that, when feeding that very limited set of results into the Elo formula, it thinks Muguruza’s level is close to that of the best player in the world.
Well… the best player in the world right now. There’s no truly dominant force in women’s tennis at the moment, so we’re not seeing players at the top end of the all-time Elo scale. In regular Elo, peak Martina Navratilova and peak Steffi Graf topped 2600, more than 400 points above Osaka’s current rating of 2189. It will not surprise you, then, to learn that Navratilova, Graf, Serena Williams, Chris Evert, and many others put together 22-match runs* that make Muguruza’s 2021 season look positively pedestrian.
* yes, I know how ridiculous it is that this whole article is based on the arbitrary 22-match time span. We could do the same stuff with the more natural-sounding 20-match span, but there wouldn’t be an intuitive way to fit Muguruza’s current run into the discussion. And let’s face it, 20 is just as arbitrary as 22.
Out of my entire database on women’s tennis results going back to 1950 or so, about 100 women have enjoyed a 22-match run that outscores Muguruza’s best. The top of the list is the end of Navratilova’s 1983 season, which is worth a yElo of 2445. Close behind is Monica Seles, who reached 2438 with a streak starting at the end of 1992 and extending into the 1993 season. Three more women topped 2400, another 27 exceeded 2300, and 46 more put together 22 consecutive matches worth at least 2200.
Here are the 15 active women who’ve played at least as well as Muguruza for their best 22-match spans:
yElo Player W-L Year(s)
2389 Serena Williams 21-1 2001-02
2386 Venus Williams 22-0 2000
2335 Kim Clijsters 20-2 2002-03
2332 Victoria Azarenka 22-0 2012
2234 Vera Zvonareva 18-4 2008
2217 Svetlana Kuznetsova 19-3 2004
2217 Naomi Osaka 20-2 2019-20
2209 Samantha Stosur 20-2 2010
2205 Petra Kvitova 19-3 2011-12
2205 Simona Halep 20-2 2018
2196 Caroline Garcia 18-4 2017
2186 Ashleigh Barty 19-3 2019
2180 Angelique Kerber 18-4 2015-16
2174 Carla Suarez Navarro 18-4 2015
2172 Garbine Muguruza 17-5 2015
With the caveat that I haven’t spent much of my life thinking about the best 22-match runs in women’s tennis history, this seems like a credible list. I particularly like how yElo manages to consider strength of opponent to the point that an 18-4 run*, like Zvonareva’s in 2008, can outrank so many 20-2s. (Vera even beats a few 22-0s from the amateur era.)
* the link shows a few extra matches–the 18-4 run starts in the QFs of Guangzhou and ends in the Tour Finals semi-final. Note again that yElo skips retirements.
I hope you find the new yElo metric as interesting as I do. I’ll definitely be doing more with it, since I suspect it has value even outside the narrow context of one player and a single timespan of arbitrary lenth.
