Discussion on several 'urban myths'
Hopefully across the first two parts of the Tennis Betting Masterclass I've given readers some useful insight in how to assess player ability, and how a player's stats have the potential to change based on the quality of opposition they face, but now I want to move on to some of the other methods that some bettors use to assess a player's chances of winning a match, some of which may be a little over-valued.
Difficult to give most head-to-head records much consideration
The first area that I want to discuss briefly is head-to-head records between two players. Often you might see this pop up on a screen in advance of a match, and commentators frequently refer to it as it's a matter of considerable importance. However, my view is that this is by and large, absolute nonsense. My previous research also illustrated as much. Certainly, a 1-0, 2-0, or 2-1 head-to-head lead is absolutely meaningless. Before attaching any relevance to previous meetings at all, I'd want to see a 3 match or greater lead, ideally over the last 2-3 years at the most, surface relevance and also a similar context between the previous results and today's match-up, from a ranking and general ability perspective.
Needing to hit these four requirements mean that it is very difficult indeed to find an imminent match-up where previous head-to-head results would hugely influence my thought process. It's not impossible, but it certainly doesn't happen very often.
Head-to-head context is key
I'll finish on this subject by recounting a story told to me by a now-retired former top-10 ATP player. He had a significant head-to-head disadvantage over one particular player on tour (who will remain also un-named), but he said to me words to the effect of 'yes, I had a really bad record against him, but every match I walked on court confident I was going to win. If you look at what happened in those matches, you'll see that I had match points, was serving for the match a couple of times, and other times lost critical tiebreaks'. The point he made to me was absolutely critical - context is key. He lost a number of matches where he could easily have won, and even this 'dominant' head-to-head deficit that he faced from a basic head-to-head scoreline wasn't nearly reflective of the actual match-ups.
Confusion surrounding home advantage in tennis
Funnily enough, this match-up was between two players from the same country, which neatly leads me on to the next 'urban myth' - home advantage in a tennis match. The home team or player can derive considerable benefits in many sports, with for example, the home advantage in football a well-known phenomenon.
Some bettors actually consider this 'a thing' in tennis as well, and to some extent I agree with them, although probably via a rather different thought process. A player probably will have marginally better results in home conditions against the average player compared to non-home conditions, but my reasoning here focuses on the greater likelihood of them having conditions more to their liking at home. For example, a traditional clay-courter, who often comes from countries such as Spain or Argentina, will also find a number of clay tournaments in their home country, many of which will be played in pretty slow conditions - likely to suit the average clay-courter over the average opponent.
So, I'd argue that it's not the specific country that is the most relevant factor here, with the actual venue conditions more likely to favour home players. What is also worth mentioning is that an efficient market should, in theory, be able to adjust accurately for any potential home advantage, if it actually exists.
Focusing on likely venue conditions a better plan
What I did was go through all the home matches played by players in the current top 100 at ATP 250 level or above from the start of 2019 onwards, which derived a sample of just over 600 matches. Based on closing prices, these players were expected to win 360.76 matches, and they actually won 367 - so they won 6.24 more matches than closing price expectation.
This sounds good, but there's several factors which would suggest that this isn't worth getting excited about. Firstly, the current top 100, by definition, should feature more players on an upward curve than a downward one (because those on a bad downward curve may have dropped out of the top 100 in the period between the start of 2019 and now), but also because winning 6.24 more matches than closing price expectation from a sample size of 600 matches (just over 1% above expectation) would suggest that on average, the market isn't hugely inefficient at all - the closing prices weren't far out. Blind-backing all home players isn't likely to yield much in the way of returns. I would recommend focusing on conditions likely to suit a particular player's skill-set (e.g. venues which are likely to feature very fast or slow conditions) as opposed to worrying on the actual country where the match takes place.
After-effects of a notable underdog win
The final area which I want to look at is the after-effects of a big win, where a player records a really big underdog victory - in some cases a career-best triumph. This can also manifest itself in the outright markets, with some incredible over-reactions taking place in recent years.
Several notable examples of this include Lukas Rosol, who at Wimbledon in 2012 shocked Rafa Nadal in the second round when ranked around the 100 mark. Quite bizarrely, he was then chalked up as the fifth-favourite to win the title on the Exchange, despite the fact that he was an underdog against Philipp Kohlschreiber in the third round. The outright market was punished when Kohlschreiber eased to a comfortable straight-set victory.
This was also the case for Cori Gauff at Wimbledon last year, and also at the Australian Open this year as well. Gauff entered Wimbledon as a 15 year old qualifier ranked outside the top 300, but after a third-round win over Polona Hercog, where she was fortunate to progress (she saved two match points), she was somehow priced at around the 27.026/1 mark to win the event needing to win four further matches against high-level opposition. In Melbourne in January, she defeated Naomi Osaka when a heavy underdog, and was backed in to fifth-favourite for the tournament ahead of her match with Sofia Kenin. Kenin was actually a bigger price to win the tournament, despite being a favourite to win their fourth-round clash.
On all three occasions, the player over-valued by the outright market was defeated in their next match, so I thought it might be both interesting and useful to try and perform a slightly more in-depth study with a view to help readers understand the after-effects of a big win - can these players carry on their good 'form' or high level into the next match, or did they struggle to replicate this, potentially due to fatigue (possibly either physical or mental, or even both).
Heavy underdog winners below expectation in their next round
The reality is that it is very difficult to get big sample sizes of relatively recent data in this area. I extended analysis back to the start of the 2018 season for this, and still I only found 58 instances of current ATP Top 100 players winning a match with a subsequent round still to play (e.g. not a final) when having a closing price of 5.00 or greater.
While this sample size was obviously small (and shows how rare wins in this price range actually are) it wasn't positive for players in their subsequent match after a heavy underdog victory. Expected wins (based on closing prices) from these 58 matches were 20.83, while actual wins were only 19 - a negative difference of -1.83 (just over 3% worse than expectation).
Despite this sample size being pretty small, it is difficult to particularly have any confidence in a view that these players, after a big underdog win, are undervalued again in their subsequent match. Also, as I've indicated with the examples above, there may also be some opportunities in the outright markets to oppose players who are overvalued due to a high profile win.
Follow Dan on Twitter @TennisRatings
Be sure to check out the other volumes in our Betting Masterclass series, listed below:
Volume 1 - Ed Hawkins on Test Match Cricket
Volume 2 - Ed Hawkins on Twenty20 Cricket
Volume 3 - Ed Hawkins on how to bet on ODI Cricket
Volume 4 - Mark O'Haire on the football stats that don't matter
Volume 5 - Mark O'Haire on benefits of data and beating the closing price
Volume 6 - Mark O'Haire's perfect football punt checklist
Volume 7 - Steve Rawlings on how to make golf tournament bets
Volume 8 - Tony Calvin on how he makes racing profitable
Volume 9 - Kevin Blake on the importance of the skill of race reading
Volume 10 - Mike Carlson on betting on NFL
Volume 11 - Dan Fitch on getting the maximum from your darts betting
Volume 12 - Paul Krishnamurty on how to make your snooker bets pay
Volume 13 - Dan Weston on assessing player quality on the ATP Tour
Volume 14 - Dan Weston on the impact of opposition quality