We have reached the final weekend of the 2025 Australian Open. Aryna Sabalenka, Paula Badosa, Iga Swiatek, and Madison Keys will battle it out to see who takes home the first Grand Slam title of the season.
For two of these players, there is even more on the line: Iga Swiatek and Aryna Sabalenka each could be the World #1 at the end of this tournament. If Sabalenka makes it farther in the tournament than Swiatek, she will retain her perch atop the rankings – and she would likely remain there through the entirety of the Grand Slam season. Looking at what comes next in the schedule, Iga Swiatek has 5 titles to defend between now and the middle of June (Doha, Indian Wells, Madrid, Rome, and Roland Garros), while Sabalenka has just 1: the Australian Open. While neither has any rankings points from Wimbledon, Sabalenka is a better grass-court player than Swiatek, giving her an advantage in the rankings all the way through Cincinnati, the week before the US Open.
Let’s look at the Australian Open women’s semifinals by reviewing how our models evaluated each player’s journey through the draw and endin with a prediction for each match.
(1) Aryna Sabalenka vs (11) Paula Badosa
Coming into the tournament, we had Paula Badosa on our list of at-risk seeds, with a caveat. We mentioned that if she made it through her first-round match, there was not a lot of resistance between her and the second week. Once she got there, she put together two impressive performances against Olga Danilovic and Coco Gauff to reach her first career Grand Slam semifinal. Badosa has been very good behind her serve, putting up a Serve Excitement Average below the tournament average in every match except for her third-round encounter with Marta Kostyuk. She has also used her return to create big buffers for herself, especially in big moments. In every match, she has either converted over half of her break points or had at least 10 of them. Combining these two trends, she has held at least 72% of her service games and broken in at least 35% in every match this tournament.
Two-time defending Australian Open champion Aryna Sabalenka is very comfortable in the Australian Summer, having lost just one match and won 4 titles in the country since 2023. This year, however, she has not been her same dominant self. In the quarterfinals, she lost her first Australian Open set since the second set of the 2023 final. She has also held serve in less than 70% of her service games in 2 of her 5 matches. There are, however, indications that her typical results are still possible. CFOE ratings in victories tend to regress to 2, so anything below 2 is likely to improve over time while anything above 2 is likely to come back down to earth. In 3 of Sabalenka’s 5 matches, her Serve CFOE Rating was below 2. The return, on the other hand, has not been a problem. Sabalenka has created numerous opportunities, with a Return Excitement Average above the tournament average in all but one match – her Round of 16 match against Mirra Andreeva in which she won more points on Andreeva’s serve than Andreeva herself. She has also broken serve in at least half of her return games in every match.
Each of these players has been excellent behind their return in creating opportunities for themselves. Sabalenka loves to pounce on a second serve, and Badosa has not yet made 70% of first serves in a match. But Sabalenka’s serve is a candidate for positive mean regression. For Sabalenka to make her 5th consecutive Hard Court Major Final, that mean regression will have to happen quickly, and it will have to coincide with a similar mean regression for Badosa’s return.
Prediction: Sabalenka in 2. Our model has Sabalenka’s win probability at 81%. Below are the predicted outcomes
(2) Iga Swiatek vs (19) Madison Keys
Coming into the tournament, our modeling was very high on Madison Keys. She was 4th in initial title odds at 8.7%, and she has continued to impress from there. Keys has lead with her serve, with a Serve Excitement Average better than the tournament average in all but 1 of her matches. I do, however, have some concerns about the stability of those numbers. While she has held serve at a rate over 90% in 3 of her matches, it has been under 70% in the other 2. And her Serve CFOE – a metric which, as previously mentioned, regresses to 2 – has not yet dipped below 4.3 while going over 9 twice. And she has not had the production behind her return to back it up. Her Serve Excitement Average and Return Excitement Average have been similar to each other, and while she is due for a positive mean regression in Return CFOE, she has not yet broken in 40% of her games in a match.
Iga Swiatek has blasted her way through the Australian Open. She has been broken just twice, while facing only 6 break points. And she has broken serve in at least 5/8 of return games in each of her last 4 matches. While Emma Navarro was able to make some headway in Swiatek’s service games, everyone else was unable to even make a dent, with Serve Excitement Averages multiple standard deviations below the mean (lower is better on serve). At the same time, she has had Return Excitement Averages multiple standard deviations above the mean (higher is better on return). She has played just 473 points over 5 matches, over 300 less than Keys’s 810 points in the Australian heat.
To win this match, Madison Keys will likely have to reach her top level for an extended period of time and win a significant proportion of the big points on her own serve. She has done it before, but it will not be easy.
Prediction: Swiatek in 2. Our model has Swiatek’s win probability at 79%. Below are the predicted outcomes.
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