Getting to the 2018 WTA Finals--An Elo Story

The 2018 WTA Finals is upon us. With Simona Halep bowing out of the event, Caroline Wozniacki enters with the highest GIG Elo Rating. But what do the ratings trajectories of the 8 competitors reveal about who could have the most momentum and confidence heading into Singapore?

The chart below tracks the ratings over the past 12 months for the 8 players who will compete for the WTA Finals title. Although Halep is out, I’ve included her trajectory as a reference for what might have been. The thing that immediately jumps out from this chart is how much change the ratings of most of the players have undergone this year.

In fact, 5 of the 8 have seen a change of more than 100 ratings points between now and this time last year. For 4 of those players—Angelique Kerber, Naomi Osaka, Petra Kvitova, and Kiki Bertens— the change is all to the good. Osaka and Bertens are the two most improved over the 12-month period, Osaka gaining 188 ratings points and Bertens 192 points over that period. Svitolina has had the most of a downturn, dropping 172 points from where she was before the group stage in 2017.

Trajectories as dynamic as those above tell us that there have been a lot of surprises at the top of the WTA Tour this year, with most of the strongest players at the moment showing they were better this year than we expected at the start of the season. The breakout seasons of Osaka and Bertens being the most notable in this respect.

But the change from one year ago to today is really only part of the story. It is also interesting to see what their peak rating was in the past year and how recently that highest 2018 rating was achieved. The chart below highlights this milestone and places it along side each player’s rating from one year ago, showing how far each has come, and each player’s current rating, showing how close each currently is to her best this year.

Only one player is currently at her peak level, and that is Naomi Osaka. The three players to have peaked most recently, aside from Halep, are Kerber, Stephens and Bertens. Pliskova has been the most steady of the group, while Svitolina and Wozniacki have had a string of disappointing results in the last half of the season. Still, Wozniacki recent title win in Beijing shows how quickly she is able to turn things around.

Heading into the finals two big questions will be how much Wozniacki can maintain her recently high level? and how will the first-time competitors at the finals—Stephens, Osaka, and Bertens—handle the occasion? If it comes down to momentum, Osaka has the edge; if it is about experience and consistency, expect Wozniacki to defend her title.