Ranking Feature
Forecasting the USTA Clay Court Nationals
by Dallas Oliver, 10 July 2015
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As we get to the heart of summer, the USTA junior competition calendar is building momentum. This coming week, the first USTA Gold Balls of the summer season are available at the USTA Clay Court Nationals - where many of the nation's elite will compete for national titles.
So, who are the favorites? Which seeds have the toughest first-round draws? How many upsets should we expect? Fortunately, Tennis Recruiting is here to answer some of these questions...
Introducing the Power Rating
Every week, Tennis Recruiting publishes the Head Boys' Class Rankings and the Babolat Girls' Class Rankings - which rank American tennis players in their graduating classes. But behind these lists are raw number values that our ranking system assigns to individual players based on their results - values that we call the Power Ratings.
Every boy and girl in our system has a power rating, and these power ratings have interesting mathematical properties. In particular, we can estimate the likelihood for the winner of a match between two players using the relationship between their power ratings. We have never done much publicly with these power ratings in the past, but that is all about to change.
Clay Court Heat Maps
Today we make use of these power ratings to produce USTA Clay Court Nationals Heat Maps that provide projections for these elite junior tournaments, which you can view by clicking here. These heat maps are inspired by similar maps and charts on websites like FiveThirtyEight, which offer predictions for larger events like the NCAA Basketball Tournament and the World Cup. We believe that these heat maps provide the first projections ever available for junior tennis. We plan to provide heat maps and forecasts for all of the Clay Court Nationals - adding tables for the various age groups as draws become available this weekend.
The Clay Court heat maps use our power ratings to come up with probabilities for how far we expect each player to progress through the draw. The depth of red in the table next to a player illustrates how likely it is for that player to advance. We will update the heat maps after each round of the tournaments to reflect the new estimates based on actual wins and losses.
After you click through to the heat map, there are many interesting ways to explore the data:
- At the very top of the table, there are tabs that let you choose from among the eight age/gender divisions.
- At the start of the tournament we show our initial predictions, but we will provide updated predictions as the tournament plays out. After the tournament starts, you can click to see our predictions at any point along the way - going back to our initial predictions.
- You can sort by any column in the table, and most of the available sorts are interesting. Sort by draw line to get a good initial view. Sort by seed to see the seeds who have the toughest roads. Or sort by a round to see who has the best chance of advancing to that round.
Predicting Upsets
One other interesting thing to note is the Upsets Section at the top of the table. Since most matches are competitive, there is a significant chance that the higher-rated player will lose - particularly when we look across a large number of matches.
As an example, consider the top sixteen seeded players in the Boys 16 Singles. On average they have a 82% chance of winning their first matches. Our projections have all of the seeds winning if you look at them individually, but when considered as a group we expect that two or three of those seeds will lose their first match. In fact the odds of
all of these seeds winning their first match is less than 3.5%.
To drive the point home even further, consider that in the Boys 14 Singles we estimate that the chances of every higher-rated boy winning his first round match is less than one in a hundred million. Having a hard time wrapping your head around that number? Consider this - the chance of an average person living in the US being struck by lightning is 115 times more likely than the odds that there will be no upsets in the first round of the Boys 14 Singles. This phenomenon is why there are never any perfect brackets during any of the major bracket challenges.
Cue the Upsets Section. The Upsets Section at the bottom of each table shows predictions for numbers of upsets given the estimates in the tables. We show predicted and actual numbers for the overall number of upsets - as well as upsets of seeded players.
A Closer Look
Scattershooting through the heat maps, there are lots of interesting predictions you can make based on these estimates...
- Players with the best chance of advancing to the semifinals:
- One draw that is tough to pick is the Boys 18s. Although top seed Sam Riffice is a favorite to win the tournament, twelve different players have a strong chance of winning the gold ball. And all players have challenges to overcome prior to reaching the semifinals.
- Top seeds with the toughest road to the semifinals:
- Two draws with interesting first-round matchups are the Boys 14s and Boys 16s. We predict a whopping fifteen upsets in the first round of both of those tournaments. In the Boys 14s alone, there are eleven first-round matches between closely-ranked players where we believe the outcome is close to a coin toss.
These are just a few of the interesting predictions you can explore using different sorts of the data.
No One Can Predict the Future
These forecasts are intended more for the interested spectator to follow along as the tournament proceeds, but if you are a participant please don't let the colors discourage you. These estimates are just numbers a computer assigns based on win/loss records we have in our system before the tournament begins, and they adjust week to week based on your play. We think that our numbers are correct across many people, but we can't predict the future any better than the weatherman - and we expect the underdogs to win many matches.
Also, even if our numbers say you have a very low chance of defeating your opponent, there is very little downside to playing and losing. But there is huge upside potential to playing and winning.
Consider, for example, the No. 1 seed in the Girls' Singles at Wimbledon. Our system gave her a 98% chance of winning her first-round match. The top seed also had a UTR that was 1.51 points higher than her opponent - and she was ranked No. 1 by the ITF with 935 singles points compared to a No. 1,148 ranking and 25 singles points for her opponent. Every measure of this match-up by every ranking system predicted an easy win for the top seed... but she ended up losing 1-6, 2-6. That is what makes sports so intriguing.
Follow Along!
So that's it. As the tournaments move along, we will update our estimates and predictions. Check out the upsets - and cheer on the players who move further than their power ratings might suggest. We expect there to be quite a few upsets - that's why they play the game!
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