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Sep 20, 2018
Sep 20, 2018

Betting market analysis of grass court tennis matches

How accurate are odds for grass court matches?

Is there value betting on underdogs on grass?

Do more big upsets occur at Wimbledon?

Betting market analysis of grass court tennis matches

It’s common knowledge that the surface of a tennis court will have an impact on how a player performs. However, while bettors will already likely consider what it does to a player, they also need to be wary of what it does to the market itself. Do favourites or underdogs offer more value on grass? Read on to find out.

Across the ATP and WTA, just 14 of the 126 tournaments scheduled for 2018 are contested on grass courts. Compared to the 75 and 37 tournaments on hard and clay respectively, the grass court swing is by far the shortest.

Is the market adept at pricing matches over this short grass court season? This article explores if pricing of grass court tennis is well understood and whether favourites or underdogs provide better betting opportunities for bettors on this surface.

How do underdogs fare on grass?

Since 2010, underdogs have won 29% of grass court matches, compared to 30% on both hard and clay. Interestingly, the average odds of a winning underdog was considerably higher on grass - 3.33 compared to 3.11 and 3.13 on hard and clay respectively. This suggests that there have been some big price underdogs that have won matches on grass. Indeed, for winning underdogs, 1.7% had odds over 10.00 on grass compared to just 1.2% for non-grass matches.

When we compare Pinnacle’s odds implied expectations and match win percentages on grass for players with odds over 10.00 (implied probability less than 10%), their odds appear to be well calibrated. Pricing suggests we should expect 6.4% of these players to win, of which 5.8% (ATP) and 6.3% (WTA) do so.

grass-court-betting-analysis-inarticle1.jpg

Pinnacle odds do appear to be efficient at all prices. The only odds ranges where player win percentages exceed expectation by a considerable margin are for WTA players whose odds are between 5.00 and 10.00 (implied probability 11-20%) and ATP players whose odds are between 1.43 and 1.67 (implied probability 61-70%). The table below shows returns to a strategy of betting a fixed amount on every grass court player within each implied probability range.

Betting a fixed amount on every grass court player

Implied probability

Odds range

ATP bets

Average odds

ATP return

WTA bets

Average odds

WTA return

0-10%

> 10.00

223

16.30

27.40%

95

14.20

-11.30%

11-20%

5.00 - 10.00

448

6.65

-9.60%

271

6.53

5.10%

21-30%

3.33 - 5.00

534

4.00

2.80%

460

3.93

-4.10%

31-40%

2.50 - 3.33

572

2.86

-11.10%

606

2.86

-4.40%

41-50%

2.00 - 2.50

575

2.23

-4.80%

588

2.24

-6.20%

51-60%

1.67 - 2.00

562

1.81

-0.30%

561

1.80

-2.30%

61-70%

1.43 - 1.67

592

1.53

1.60%

620

1.54

-0.60%

71-80%

1.25 - 1.43

505

1.34

-2.90%

491

1.34

-1.40%

81-90%

1.11 - 1.25

483

1.18

-2.90%

322

1.18

-2.10%

91-100%

< 1.11

342

1.06

-1.40%

150

1.07

-2.60%

The highest return (27.4%) would have been generated by betting on all ATP players with odds greater than 10.00. This is despite the actual win percentage being lower than the average win percentage implied by the odds. So what’s going on here?

Wimbledon is the only grass court tournament with a 128 player draw, meaning the early rounds will often throw up lopsided contests, but equally, opportunities for some big upsets.

Of the 223 ATP grass court players with odds greater than 10.00, only 13 of these won (5.8%). A profit was generated because their prices were skewed towards higher odds when compared to the players that lost - 31% of those that won had odds greater than 30.00 compared to just 15% of those that lost.

Since 2010 there have been four grass court matches where underdogs won having odds greater than 30.00. They all occurred at Wimbledon and were all ATP matches. The biggest priced WTA upset was Larcher De Brito (24.52) beating Sharapova in the second round in 2013.

Wins by underdogs at greater than 30.00

Tournament

Pinnacle odds

Player

Opponent

Score

Wimbledon

46.00

Sergiy Stakhovsky

Roger Federer

6-7, 7-6, 7-5, 7-6

Wimbledon

41.00

Lukas Rosol

Rafael Nadal

6-7, 6-4, 6-4, 2-6, 6-4

Wimbledon

34.00

Steve Darcis

Rafael Nadal

7-6, 7-6, 6-4

Wimbledon

31.30

Sam Querrey

Novak Djokovic

7-6, 6-1, 3-6, 7-6

Wimbledon

24.52

Michelle Larcher De Brito

Maria Sharapova

6-3, 6-4

Wimbledon

20.00

Ernests Gulbis

Tomas Berdych

7-6, 7-6, 7-6

That all the big recent grass court upsets have occurred at Wimbledon is no surprise really. It is the only grass court tournament with a 128 player draw, meaning the early rounds will often throw up lopsided contests, but equally, opportunities for some big upsets.

Wimbledon has seemingly become famous for them. From Nadal being knocked out by Rosol (41.00) and Darcis (34.00) in consecutive years, to Federer losing to Stakhovsky (46.00) in 2013, and Serena Williams falling to Lisicki (10.25) in the same year, some of the biggest tennis upsets in recent memory have occurred at the All England Club.

The tournament has also seen some big longshots go all the way. Who could forget Ivanisevic’s 2001 triumph as a wildcard or Sharapova winning in 2004 as a 17-year-old?

Do more big upsets occur at Wimbledon?

In this decade underdogs have won 21.7% of ATP and 26.9% of WTA matches at Wimbledon, more or less in line with the other Grand Slams. The tournament does have a higher proportion of big ATP upsets however, with 4.6% of players with odds over 10.00 winning.

ATP Upsets by grand slam

Grand Slam

ATP upset %

ATP average upset odds

5.00 - 10.00 upsets

10.00+ upsets

Wimbledon

21.70%

3.02

11.10%

4.60%

Australian Open

21.90%

2.93

11.40%

3.20%

French Open

19.10%

2.99

9.10%

4.30%

US Open

24.60%

3.04

16.20%

3.30%

WTA Upsets by grand slam

Grand Slam

WTA upset %

WTP average upset odds

5.00 - 10.00 upsets

10.00+ upsets

Wimbledon

26.90%

2.89

13.40%

6.60%

Australian Open

26.90%

2.81

15.20%

2.30%

French Open

26.40%

2.86

10.20%

8.10%

US Open

26.70%

2.96

17.50%

6.20%

WTA Grand Slam matches consistently produce more upsets than ATP matches. This can be partially explained by the fact that they are contested over best of three compared to best of five sets. The shorter the match, the more variance in the result. Over a best of five set match, an ATP underdog is less likely to maintain a level required to beat a more fancied player.

Betting on big upsets at Wimbledon

Is a simple strategy of betting on all big underdogs at Wimbledon a good one? The table below shows returns to betting a fixed stake on all Wimbledon underdogs since 2010 in three odds ranges: 2.00 - 5.00, 5.00 - 10.00, and 10.00 or greater.

Betting on big underdogs at Wimbledon

Implied probability

Odds range

ATP bets

ATP return

WTA bets

WTA return

< 10%

10.00+

175

19.90%

91

-7.50%

11 - 20%

5.00 - 10.00

244

-27.40%

186

-11.30%

21 - 50%

2.00 - 5.00

564

-10.10%

720

-7.40%

A strategy of betting on all ATP players with odds greater than 10.00 would have yielded a return of just under 20% from 175 bets. The same strategy at the other three Grand Slams would have resulted in a significant loss, at an average of -48%. In WTA matches, betting on 10.00+ underdogs was a similarly poor strategy, except at the French Open where a return of 39% would have been generated from 111 bets.

A comparison of Wimbledon match win percentages with probabilities implied from player odds may reveal other potential odds biases. We can see in the chart below that Pinnacle’s Wimbledon prices are generally accurate across all odds ranges.

grass-court-betting-analysis-inarticle2.jpg

The exception is a bias in ATP pricing in matches where players have an implied probability between 40% and 60% (odds between 1.67 and 2.50. Slight underdogs (41-50% implied probability) win less often than they should and slight favourites (51-60% implied probability) win more often than their odds imply.

For two closely matched ATP players, the market appears to correctly identify the favourite but doesn’t price them as short as they should be. A strategy of betting on all Wimbledon favourites with odds between 1.67 and 1.95 (51%-60% implied probability) would have returned a profit of 6.0% since 2010.

Betting at Wimbledon 2018

This article has shown that despite only comprising a small slice of the tennis calendar, grass court matches are generally reasonably well priced. The two biases uncovered are that betting on 10.00+ ATP underdogs and slight ATP favourites at Wimbledon have been profitable strategies since 2010. While these trends may or may not continue, Pinnacle’s low margins mean that there may often be considerable value in the prices of these players throughout The Championships.

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