The Odds Are Against Quick Comebacks
After 6 months out of action owing to an elbow injury, Novak Djokovic is one match away from a quarterfinal at the Australian Open. Djokovic is on track to make a strong return in Melbourne. But how unusual is a fast comeback after injury? What can most top players who have delayed their 2018 return expect about the difficulty of reaching their previous form?
As exciting as the first week of the Australian Open has been, a number of top male players looked rusty in their first matches and seven of the top 30 weren’t able to advance beyond the first round, including the 8th and 11th seeds Jack Sock and Kevin Anderson.
By the third round, only 5 of the top 10 ranked players remained in the draw while 5 spots unexpectedly went to players outside of the top 30.
The opening up of the men’s draw has created great opportunities for players who haven’t been in the spotlight of a Major before, including young start Hyeon Chung and journeymen like Tennys Sandgren and Marton Fucsovics. But we can’t overlook that these opportunities have a lot to do with an outbreak of injury that struck the top of the game in 2017.
Both Rafael Nadal and Novak Djokovic entered the Australian Open draw with a lot of uncertainty about their form. Nadal has settled most doubts about his fitness with his strong performances in the opening rounds. Djokovic has advanced but their have been clear signs that his game has adapted to his elbow injury, as his service pace and patterns have been notably altered this year.
Other top players have had less success making their comeback. Stan Wawrinka was clearly struggling with his leg movement in his second round loss to Tennys Sandgren. Even more troubling were Kei Nishikori and Andy Murray’s announcements that they wouldn’t be competing in Melbourne at all.
Among this small sample of players, the prospects of a strong comeback are clearly mixed and make the shape that the 2018 men’s tour is going to take very uncertain.
What can the past tell us about how well top players bounce back from an injury break?
Since the 1990s there have been 28 men’s players who were in the top 10 and had a gap in play of 90 days or more. This group is the best placed to give us an idea of what the typical comeback looks like for a top player after a notable gap in play.
Using player Elo ratings in the 30 matches before their break and the 30 matches after, we can see how well they performed in the pre-gap and post-gap period. Each player’s rating is compared to their baseline at the start of the pre-gap period, so a 0 would mean they are playing equal to their level before the absence.
The overarching trend is for players to struggle in their first year back with most losing more than 50 Elo rating points in the first 6 months of their return. That decline equates to an approximate drop in win expectations of 5 percentage points. It is also notable that a downward trend just before the gap is common, suggesting that players drop in performance prior to a major gap.
Not All Returns Are Equal
Although the above cloud of points in the pre- and post-injury period suggest a negative impact during a return, to be confident in that trend we have to link the pre- and post- trajectories for each individual player. Below is an example of what one player trajectory looks like.
2017-18 wasn’t the only period that Andy Murray had a major gap due to injury. At the end of 2013, he also took time out from his season to address a back injury. When Murray returned, his rating took a stark dive in the initial months.
When we apply a hierarchical model to these data, it turns out that this is the stereotypical pattern. Thus, even top players are not likely to bounce back immediately when they return to play after a physical issue.
Although a decline is the most likely trend to expect after injury, it isn’t every players fate. In rarer cases players have excelled immediately after a break. We all remember the rise in Nadal and Federer’s results coming back from breaks at the start of 2017. And in our historical sample, Andre Agassi, current coach of Novak Djokovic, had an impressive return in 2001, sandwiched between two other major breaks in his career where getting back was more of a struggle.
This analysis suggests that a resurgence of the Murray-Djokovic rivalry in 2018 might not be coming in the near future. But there are some considerable drawbacks to our current data around injury that make it difficult to make any strong predictions. First, we aren’t able to factor in the type or severity of injury other than through the length of a gap. Second, we know nothing about a player’s training or recovery regime that could help or hinder their comeback prospects. Until we have better ways of describing the nature of injury and training variables, we should be cautious to assume that any one player will follow the same comeback trends of the past.