Do Underdogs Have an Edge on Grass? 2,712 ATP Matches Analyzed
Favorites returned -3.2% and underdogs +1.1% across 2,712 ATP grass matches before Wimbledon. Not a profitable angle, but a gap worth monitoring.
Have you ever wondered whether betting results for underdogs and favorites are particularly different on grass?
Well, I used Favordog to find out.
Why Wimbledon Is Excluded
I separated best-of-three matches from best-of-five matches (Wimbledon). As I've said many times, betting patterns in BO3 and BO5 are completely different, so I always recommend splitting this type of analysis between Grand Slams and the rest of the tour.
In Grand Slams, average odds tend to be higher because the quality gap between the two players is usually larger. This tends to intensify the favorite-longshot bias and, although there are some exceptions, underdogs generally lose heavily in the long run.
The Results: 2,712 Matches Since 2010
So I took all grass-court tournaments played before Wimbledon since 2010, and these are the results:
- ROI Favorites: -3.2%
- ROI Underdogs: +1.1%
(Pinnacle closing odds, 1-unit stakes)
Is This Profitable?
Can we say that betting on underdogs in BO3 grass events is profitable?
No.
First, a 1.1% yield, even across more than 2,700 bets, is still very close to zero. Also, we can see that the best ROI comes from the longshot range, meaning that a handful of big-priced winners could be driving the positive result.
A Relative Bias Against Favorites?
However, what does seem possible is that there may be a relative bias against favorites and in favor of underdogs in these tournaments.
The difference between the two groups is 4.3 percentage points, in 2,712 bets, which is substantial. In fact, based on a rough statistical estimate, this gap is not large enough to be considered statistically significant at conventional levels, but it is still large enough to be interesting and worth monitoring.
The unique characteristics of grass courts, the limited amount of tennis played on the surface, and the possibility that the market does not fully price in that additional uncertainty could all be contributing factors.
So be careful with Favorites in grass tournamente pre-Wimbledon.
