Is Slam Momentum a Thing?

With two heavy outsiders into the men’s semifinals, does the outcome of the men’s draw become a foregone conclusion? Or should momentum raise our expectations for the underdogs?

One of the most fascinating stories of the 2018 Australian Open has been the breakthroughs of a number of unlikely contenders on the men’s and women’s draws. Some of those surprises, like Tennys Sandgren and Hsieh Su-Wei, are out of the event, while others are continuing their journey. On the men’s side two unseeded players, Hyeon Chung and Kyle Edmund, have reached the semifinals, both personal bests at a Major event. On the women’s side, Elise Mertens has done the same as the only female semifinalist outside of the top 30.

For underdogs, going deep into a slam requires an incredible run. And odds would suggest that such a run is more likely to end than continue, making the chances for the pre-event favourites that much greater. But if you listen to commentary it would seem the opposite, as commentators love to back (or at least raise the odds of) the player who has the “momentum”.

So which perspective is right? Is it enough to look at who a player has won and lost to in the past to predict their future performance? Or should we consider whether a player has gotten “hot” over a short period and boost their expectations even more?

Who Has the Momentum

If we compare the Elo ratings progression among the men’s semifinalists, we can see that, if anyone has momentum going into the final days of the Australian Open, it’s Kyle Edmund and Hyeon Chung. Since the start of the year, both Chung and Edmund have gained over 100 points in their Elo rating, most of that rise coming from their gains at the Australian Open.

For Federer and Cilic, the picture is very different. They have been favourites (often heavily so) for all of their Australian Open matches so far. So while they gain with each win, the jumps are much smaller because they are playing to what was expected.

For the women’s draw, Elise Mertens is the player who most came out of nowhere, having a run that is the likes of Edmund and Chung’s.

Kerber, the only semifinalist with a Major title, also has gained a lot of momentum, making her the resurgence story at the start of 2018.

Momentum Records

The chart above shows that player Elo ratings naturally adjust upward when players have a string of big wins, rising more steeply the more surprising each win was at the start. This is the process of trying to better align pre-match expectations with outcomes.

The question is whether, given a streak, do players gain momentum that should make us adjust their ratings even more?

Research on momentum, also called the ‘hot hand’, in sport has never had very certain conclusions. A lot of that has to do with the fact that momentum effects are difficult to measure, especially when small sample sizes are in play as with slam-specific momentum effects.

While not conclusive, it is still of historical interest to look at how other underdogs with similarly surprising runs have fared at past Majors.

The table below shows the 10 most impressive semifinalists at Grand Slams from 1990 to 2017, according to the gain in their Elo rating up until the semifinal. Only 2 of the 10 went on to win the slam, Gustavo Kuerten and Pete Sampras, first slam wins for both who would each go on to win multiple Major titles.

Player Year Event Won Title SF Elo Gain
Vladimir Voltchkov 2000 Wimbledon No 260.7
Gustavo Kuerten 1997 Roland Garros Yes 191.4
Marcos Baghdatis 2006 Australian Open No 177.7
Martin Verkerk 2003 Roland Garros No 153.7
Jo Wilfried Tsonga 2008 Australian Open No 135.3
Wayne Ferreira 1992 Australian Open No 132.1
Patrick Mcenroe 1991 Australian Open No 128.1
Nicolas Escude 1998 Australian Open No 109.4
Filip Dewulf 1997 Roland Garros No 108.9
Pete Sampras 1990 US Open Yes 108.0

The top 10 most surprising slam runs on the women’s side went 0 for 10 in titles. Yet, 4 of the 10 won a Major title within years of their surprise streak.

Player Year Event Won Title SF Elo Gain
Clarisa Fernandez 2002 French Open No 206.8
Venus Williams 1997 US Open No 177.8
Alexandra Stevenson 1999 Wimbledon No 151.6
Amelie Mauresmo 1999 Australian Open No 144.6
Mirjana Lucic Baroni 1999 Wimbledon No 120.5
Petra Kvitova 2010 Wimbledon No 116.4
Sabine Lisicki 2013 Wimbledon No 112.6
Kiki Bertens 2016 French Open No 109.3
Anna Kournikova 1997 Wimbledon No 105.3
Angelique Kerber 2011 US Open No 101.7

Even those players who didn’t get the slam trophy during these runs had, by and large, great success in their careers and should be recognisable names to most tennis fans. As Edmund, Chung and Mertens have all reached the same milestone with similarly rapid gains in their ratings, they have already put themselves in an elite class of players.

Whatever happens this week in Melbourne, the forecast for their careers looks bright.

Stephanie Kovalchik avatar
About Stephanie Kovalchik
Tennis Data Scientist at the Game Insight Group at Tennis Australia and researcher at the Institute of Sport Exercise and Active Living at Victoria University.
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