Seeding Errors

The next post shows the effect of different methods of seeding a tourney like the upcoming Western and Southern Open tennis tournament. But the experiment assumed that the seeding perfectly reflected the actual skill of the various players.

We know that this is not what happens in real life. The ATP points on which seeding is based do tend to correlate with skill – the whole seeding regime would be pretty pointless if they did not. But that’s not all that the ATP is trying to accomplish with their points. ATP points are not just a reflection of skill, but a reward for playing.

Certain players of undoubted skill, especially those who have missed a lot of recent tournaments, have relatively few ATP points, and thus relatively low rankings. Andy Murray has been away from the tour so long that he needed a special “wild card” exemption to even make the W&S field. Like Murray, Novak Djokovic has also been recovering from injury, and will also enter the W&S unseeded.

How much does this gap between a player’s seeding based on ATP points and his or her actual skill affect prospects for success? Some effects are dramatic – as I’ll show below, Novak’s low seeding will cost him, on average, nearly $100,000.

Here are the sixteen best players currently scheduled to play in the W&S as judged by the average odds that are offered on their chance to win the U.S. Open, along with their seeding rank, and what that means for their actual seeding in the W&S. At the bottom of the list, I’ve added those players who will be seeded, but were not among the top 16 according to the betting odds,

This table shows the expectation of each of these men, first as if they had been seeded according to the betting odds, then with their actual seeding, and the difference:

The chief victims of the seeding regime are Djokovic, Murray, and Kyrgios, all of whom would have qualified for a top-8 seeding (and thus a bye) if seeded according to the punters’ assessment of their skill. The largest beneficiaries are the players in the top 8 who get byes that they wouldn’t otherwise qualify for: Thiem, Dimitrov, and Anderson. Also getting some benefit are the players at the bottom of the list who got seeds that the skill list would not have given them.

Bear in mind that this are the average expectations from 500,000 trials, each of which had its own draw. The expectations for any particular draw will be quite different.

If, for example, Murray and Djokovic are drawn to play each other in the first round (a 2.5% chance), both of their expectations will suffer considerably because we know that one or the other will have to settle for first-round money. And in all likelihood, Djokovic’s position will be strongly negative for either Nadal or Federer, depending on which half of the draw he lands in.

Once the actual draw takes place (and any late scratches are announced), I’ll run another simulation on the actual draw so that the effects can be assessed.