Caught Courtsiding

Yesterday the BBC had an interesting radio programme about courtsiding in tennis. For the benefit of those who don’t know what courtsiding is: it’s people who sit court side (stop me if I’m going too fast) and either bet themselves, or relay that information to someone else to then place bets. As the pictures you view on TV or online are around 5 seconds behind the actual action. The odds on betfair will move before a point has been won when watching online/TV.

They are basically like High Frequency Trading firms in the financial world. They have a massive edge in terms of time, they can buy the higher price before everyone else knows that a point has even been won, and can then quickly sell the lower price back into the market. The market in this case will usually refer to a betting exchange such as Betfair. And this happens on every point in a tennis match.

If you want to check it out, the radio programme is here:

And an article from which is here:

Some of the key excerpts are:

“The purpose of us being there is that we can send back information a lot faster than TV or betting companies can get the data,” says Dobson.

That information would be fed back in milliseconds to the syndicate in London. The syndicate designed betting software for tennis which works out the probability of each player winning the match at any point and how the odds are moving in real time on the betting exchange.

Steve showed me the kind of device Dan used, a modified game console controller.

“We had an automated system whereby the point data would come in and then we would cancel any bets that we had in the market that we deemed were at the wrong price. And then we would place bets straight back into the market that we deemed were now the correct price.” he says.

The difference in getting that data first and changing the syndicate’s betting position can be worth thousands of pounds per point, sometimes even tens of thousands, and there are a lot of points in a tennis match.

This has led many other syndicates to employ courtsiders. Steve High says he has been told reliably that 75 people were at last year’s Wimbledon final, “sending information back or betting on their own”.

To put it mildly: your ordinary Joe sat at home who fancies trying to trade tennis has an incredibly hard job to have any sort of edge. The big fish in this pond have the fastest information and have programs to tell them what the correct price should be.

I used to trade tennis myself. I used to do alright, but this was back in the days before courtsiding was as prevalent as what it is now. After it was clear that any sort of edge, if I actually even had a edge on tennis, had gone, I decided to write my own program to predict the odds either pre-game or in-play.

Tennis is a really easy sport to model. If I was to succeed in this field I needed something to give me an edge. So I downloaded as much data as I could get, then calculated player A’s chance of winning a point on serve against player B, and vice versa. I broke this down further into first serve %, winning a point on first serve, winning a point on second serve etc. I also took into account aces and double faults. My program would use these factors and simulate the match as many times as I wanted, and then calculate each player’s chance of winning. It would run after each point so the calculated odds would be continuously updated depending on the game state.

After a few weeks testing, the majority of the time my program gave out the same prices that the betting market was at. If there were ever any differences between my price and the market price, it wasn’t out by much at all.

Although my tennis program didn’t give an edge in the Match odds/Moneyline market, it did provide an edge in some of the alternative markets… I’ll write a longer post in the future about my experiences of trading tennis, as I’ve got a lot more to say on this topic.

2 thoughts on “Caught Courtsiding”

  1. Courtsiding is only an issue though if you are trying to price snip, i.e. think you are beating the market because you react faster than everyone else. If you are pitting your wits against a settled market, and saying that your assessment is better than the market’s, it doesn’t affect you. But you need to factor it into your betting behaviour.

    Two essential rules of betting punters must live by:
    There will always be people with more information than you in a market.
    There will always be people with faster access to live information in a market.

    And if your model/assessment is exactly the same as the market, then you are either punting, or playing a zero-sum game with no margin, like Exchange Games.



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