French Open 2021 Tips: Deficit approach suggests Nadal is poor-value favourite

Rafael Nadal at French Open
Rafael Nadal might struggle at Roland Garros more than the market suggests

It can be hard to make the mental shift to value-based tennis punting, writes Jack Houghton, but a Rafa Nadal deficit approach to the French Open might help...

"Rafa Nadal is not the dominant physical force on clay he once was..."

The search for value

Value. An oft-used and oft-misused term. To some, it is a synonym for bigger odds, as in "Those wanting more value should consider backing Pete Sampras at 50-1".

When profitable punters talk about value, though, they mean something different, more precise. To them, value is when the odds available imply a percentage chance of an outcome that is different from the actual percentage chance of that outcome happening.

The classic way to exemplify this concept is to think of the coin toss. The chance of heads is 50%. If you received odds of 2.001/1 on heads and kept backing that outcome, you would, over time, neither lose nor win money.

Likewise, if you received odds of 1.804/5 on the outcome, you would lose money over time. Value is found when you can back the outcome at odds bigger than 2.001/1.

With the simple example of a coin toss, it's relatively easy to understand what represents value and what doesn't. When the scenarios become more complex, though, it's helpful to be able to convert odds to implied percentage chances.

To do this requires some straightforward maths. In the example above, divide 1 by 2.001/1. Then multiple by 100. This tells you that, when you see odds of 2.001/1, what you're actually seeing is an implied percentage chance of 50%.

When the odds decrease, the implied percentage chance rises, and vice versa. So, odds of 1.422/5 become 70%, and odds of 14.0013/1 become 7%.

The shift from losing money to long-term betting profitability is, for most punters, about ignoring odds in and of themselves, and instead thinking about the implied percentage chances they represent.

Thinking about the likelihood of something happening - rather than just the odds - naturally then places value at the centre of your punting.

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Why the maths lesson?

The problem for punters, of course, is that little in betting is as straightforward as a coin toss. When two tennis players compete, it is much harder to accurately assess the percentage chance of each winning.

To combat this, punters use complex - sometimes arcane - rating systems. For example, I have often written in these pages about my reliance on Elo ratings, borrowed from the world of chess, to assess the relative ability of tennis players. There are other systems available: Glicko ratings are increasingly popular, and some punters are experimenting with approaches from online gaming, such as Microsoft's TrueSkill rankings.

The complexity doesn't end there, though, as the ratings are useless without a way of converting them to odds. This is hard enough in a two-player match-up but becomes increasingly convoluted when looking at whole tournaments, with punters employing statistical approaches such as Monte Carlo simulations, which I have written about previously.

Keep It Simple, Stupid

For many recreational punters, who still want profitability, such machinations are impractical. Establishing a valid and reliable ratings' system and odds-conversion method takes time and expertise that they may not have.

However, that doesn't mean that recreational punters aren't able to adopt more disciplined approaches to their analysis that are more value-based. They don't necessarily need all the bells and whistles of a fancy ratings system.

A deficit approach

One way is to swap around your thinking.

So, rather than asking what the likelihood of something happening is, you instead ask how likely something is not to happen.

This year's French Open provides an interesting case study in this approach. Rafael Nadal (2.001/1), a human coin-toss in the tournament market, is aiming for his 14th Roland Garros title. He hammered Novak Djokovic (7.206/1) in the final here last year in under three hours, has a 91.6% success-rate on clay, and the view of many is that only some misfortune will deny him the win.

So, let's start off by assuming that he has a 100% chance of winning. Now try to quantify reasons why he won't.

What are the reasons why Nadal won't win?

Well, he's not the dominant physical force on clay he once was. He has lost twice this year, to Rublev in Monte Carlo and to Zverev in Madrid, and he has frequently lost sets and been pushed harder in his matches than once would have been the case. Let's take 30% off his chance of winning the French Open for that reduced reliability.

There are also his opponents to consider. Roger Federer's (150.00149/1) return to competitive action may not be all that significant, but Djokovic is increasingly closer to Nadal on clay than he once was, and the rising form of other players like Stefanos Tsitsipas (6.4011/2), Alexander Zverev (16.50) and Dominic Thiem (19.0018/1) mean there are fewer easier matches in the latter stages of tournaments than Nadal experienced in the past. Let's take 20% off his chance to account for this opposition.

This year, the draw at Roland Garros has not been kind to him. He is in the same half as Djokovic, Federer, and a host of other potential tricky match-ups. Another 20% for that.

Then there are the conditions of play. Reduced crowds, later matches, and the increased likelihood of closed roofs and the lower ball bounces that result will all play against Nadal. The effect of this is more marginal perhaps - what affects Nadal in this regard will affect all players - but when the conditions change at a venue where he has been so dominant, that can only be good news for his opponents. Let's call that 5%.

A valid approach?

There we have it. Our deficit approach has landed us at 25%. Converting that back to odds requires a little more maths. 1 divided by 0.25 gets us to odds of 4.003/1 - what I consider a fair price for a Nadal repeat.

You might quibble with the assumptions made and conclusions drawn during those calculations, but in many ways that is not the point. More important is that the process of taking your time and objectively assessing a bet in this way will help you adopt a value-driven mindset, which is the only way to be profitable in the long run.

For now, for me, Nadal is a lay.

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