Numbers speak in Wozniacki’s favor for the Australian Open quarterfinal against Clijsters


Dear readers, our now already famous stats expert Omair couldn’t resist the urge and found time in his busy schedule to analyse the upcoming Australian Open quarterfinal between Kim Clijsters and Caroline Wozniacki. Numbers speak in Wozniacki’s favor, but is everything in numbers? Let’s see if we can conclude something.

There are so many things you plan on doing, but you you never get to complete them. That is what happened with me, when I had planned on making a probability analysis for the Australian Open 2012, it never got complete and then I got heck of busy. Being an audit trainee no doubt has its perks of excessive late sittings and no weekends, but I just could not resist my urge to analyse the Australian Open quarterfinals, using the performance of the quarterfinalists so far in the tournament. I will be using the stats to look into the quarterfinal showing, as to who has a better shot at making the semis. Let’s first analyse Kim Clijsters and Caroline Wozniacki.

Kim got her ankle twisted in her fourth round epic battle against Li Na. Wozniacki won’t get a better chance than this to avenge her previous losses to the former world No. 1, after all it was Clijsters who denied Wozniacki the taste of her first major when she beat the Dane in the US Open final in 2009.

Wozniacki has yet to lose a set in this tournament, while Clijsters has already lost one to Li, and was on the brink of defeat in straight sets but turned it around to emerge as a winner. Thousand dollar questions are: Will Clijsters’ ankle hold to let her complete in the last Australian Open of her career? Will Clijsters have enough in tank to battle past Wozniacki who has no doubt the best defensive skills at the moment?

Clijsters is 2-0 against Wozniacki, but their last meeting at the year-end Championships in 2010 went the distance. Let us have a look at what the numbers say when we see each player’s first four matches at the Aussie Open 2012:

Wozniacki has +8% advantage in the first serves, but what is important is that although Wozniacki has higher 1st serve percentage, Clijsters’ 1st serve winning percentage is much higher than Wozniacki’s, but so are her double faults. Clijsters has been serving 4+ double faults on average in each match so far, which means losing her serve at least once in each match by only double faults.

What is more worrying is Clijsters’ ratio of winners and unforced errors. If you look at the number of winners, Wozniacki is not far behind, but if you look at the number of unforced errors Wozniacki comes out as a cleaner one by a huge margin. Clijsters has a differential of negative 24, whereas Wozniacki has a positive differential of 4. Break point conversion rate, receiving points won percentage again go in Wozniacki’s favour. The department where Wozniacki lags is the points won at net. While Clijsters has lost only one point out of her 18 net trips (95%), Wozniacki managed to win only 68% of her net trips.

Numbers are in Wozniacki’s favour and Clijsters’ twisted ankle boosts Wozniacki’s chances a lot, however, Clijsters does have a few things on her side as well:

  • Clijsters has the ability of lifting her game when really needed, and we have experienced that in the past as well.
  • Her head-to-head against Wozniacki is positive.
  • Of nine times Kim has played at the Australian Open, she has always won her quarterfinal match when she has made it to the quarterfinals. She made it to the semifinals or better six out of six times she reached the quarters.

My heart says Clijsters will win, as I am a Clijsters fan, but numbers say Wozniacki is the favorite. This makes me remeber Shakira’s (if I am not wrong) song, “Hips Don’t Lie”, “Numbers Don’t Lie”.. I will say “sometimes, numbers do lie”, that is why my heart says Clijsters will book a semifinal spot. What do you see? Who do u think will come out on top?

For a taste of Omair’s previous analyses visit the following pages:

(photos: © Neal Trousdale)


  1. Predicting a tennis match winner with past numbers is like trying to predict the next stock exchange hit with the past history! Tough. Some people think it can be done, others don’t. Note that I didn’t say that it’s like predicting the next lotto numbers which would have been the real insult to this interesting work.

  2. Although I partly agree with the comment above that it is difficult to predict a match based on numbers, it is a really well written article.

    The thing that most surprised me was how Wozniacki has only hit five less winners than Clijsters throughout the championships! Wozniacki has definitely shown more intent to go after the ball at this Grand Slam, but in the second set against JJ she did go back into her defensive shell when things got tight, which she cannot afford to do against Clijsters.

    I would have gone for Clijsters in straight sets, but with the uncertainty of her ankle injury i’m actually going for Wozniacki to win this in 3 sets. It should be an interesting match and i’m disappointed its in the middle of the night here in the UK 🙁

  3. James and Gregoire Gentil

    I agree with you in that it always is a new day and anything can happen on a given day. Why I did this was because coming into this match they are bringing a certain form in to this match, what does that form suggest??? I only intended to do this…


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