Shot charts in tennis.

Posted on February 9, 2016 by Damien Demaj

During the Australian Open this year I wrote an article for tennismash.com about the use of shot charts in tennis. Below is the intro paragraph to the article:

Shot charts are critical in understanding a player’s on court behaviour. They have become commonplace in other sports like the NBA and Soccer and are now used frequently in tennis to map shot patterns from particular areas of the court. These patterns are of particular interest to coaches and players for pre and post match tactical analysis. Here we present 2,443 shots from Kei Nishikori that were played over a period of 6 months in 2014–15 against opponents like Federer, Djokovic, Murray and Wawrinka.

You can read the rest of the article here.

Kei Nishikori. Hawk-Eye Analysis Part 2

Posted on July 12, 2015 by Damien Demaj

Earlier this Japan’s National Broadcaster (NHK) contacted me to provide analytical support for a documentary they were preparing on Kei Nishikori. Part II of the documentary went to air in Japan recently and I thought I would share a few screenshots with you of the final animations and analysis.

The analysis focused on a number of key matches Kei had played over the last 12 months including:

Wawrinka at the US Open, and Aus Open.
Murray at Madrid and the World Tour Finals
Djokovic at the US Open and Rome.

Below is a brief explanation and some examples of the analysis:

Nishikori v Wawrinka (US Open, and Aus Open)

Wawrinka made some adjustments to his game after loosing to Kei at the US Open. The above graphic shows you the balls Wawrinka directed to the deuce side of the court at the US Open.

We saw from the footage that Wawrinka was targeting Nishikori’s forehand out wide and so we ran some numbers on it. We created a simple density surface of the shot location for Wawrinka at the US Open (pictured above) and at the Australian Open.

At the US Open Nishikori was given too much space and angle on his backhand and really made Wawrinka pay hitting a number of winners of this side. At the Australian Open Wawrinka made an adjustment and targeted Nishikori’s forehand, pulling him off the court with a number of short angled forehands. Below is footage of where Nishikori ended up on a number of important points which gave Wawrinka an easy shot into the open court.

Nishikori v Murray at Madrid and the World Tour Finals

Nishikori beat Andy Murray at the World Tour Finals in 2014 but Murray was able to turn the result around in Madrid during the clay court season earlier this year. One of the reasons why was because of his serving. In particular his accuracy and depth at important points. Murray also served far fewer second serves at important points in Madrid than he did at the World Tour Finals. If you’re serving short 2nd serves to Nishikori at important points than Nishikori is going to be all over the return and you’ll be playing catch up all point!

Above is Andy Murray’s serve pattern at the World Tour Finals (where he lost).

In the purple are Murray’s serve locations at important points at the World Tour Finals. In the green are Murray’s serve locations at important points in Madrid. Check out the six short serves that Murray dropped at the World Tour Finals (these were all second serves). These provided easy pickings for Nishikori. By comparison, Murray only served 1 second serve in Madrid, and his 1st serves were much closer to the lines in Madrid.

Murray was also getting some heavy rip on his serves in Madrid which forced Nishikori to regularly hit the serve return above his shoulder making it hard for him to get any real pop on the return. Murray’s serve in Madrid made it very difficult for Kei to gain the ascendency in the rallies. Players are looking to expose Nishikori’s height particularly on the serve return where he can be very damaging. Both Murray and Djokovic (in Rome) went after this as the neat little graphic below illustrates. It shows a comparison of the average height Nishikori’s was playing his returns against Djokovic at the US Open (blue) and Rome (yellow).

We also identified that the three opponents (Wawrinka, Murray and Djokovic) played much straighter through the court against Nishikori after their losses at the US Open and World Tour Finals. The two graphics below highlight what this means for Kei. His opponents took away the angle from him on his groundstrokes and didn’t allow him to pull the trigger, particularly from the backhand corner which is one of his favourite shots.

Well there’s just a few examples of the visualisations and analysis we run for the show. Millions of data points, and hundred of hours of data mining and statistics were run in search for answers to so many questions. Unfortunately I can’t share any of the analysis in depth with you but hopefully this gives you a little taste of the some of the analysis that was completed. It was a real privilege to work with the talented team at NHK, they have an extraordinary high work ethic and seek perfection in their work. We are all extremely proud of the result.

Images copyright NHK. Do not share the contents of this web page without permission from Gamesetmap or NHK.

Kei Nishikori – Hawk Eye Analysis

Posted on April 15, 2015 by Damien Demaj

Recently Japan’s National Broadcaster (NHK) contacted me to provide Hawk-Eye analytical support for a documentary they were preparing on Kei Nishikori. I was asked to process and analyze the raw Hawk-Eye data. I teamed up with Jordan Montreuil, an animator from LA to provide high-quality 3D scenes that would support the analysis. The documentary aired in Japan on the 13th January prior to the Australian Open. You can watch the program here.

The rise in popularity of Kei Nishikori is illustrated in NHK’s documentary titled “Kei Nishikori: Trails of the Progress” (translated). The documentary explores Nishikori’s growth and development as a player.

Below are a few samples from the project. Unfortunately I can’t share too many details but I hope this gives you some idea of the work completed.

The results of the Hawk-Eye analysis were told using a series of 3D computer generated (CG) animations. The images above are stills taken from the story surrounding Djokovic’s shot depth against Nishikori at the World Tour Finals.

For each scene, storyboards and animation concepts were drafted in order to understand how the story would unfold.

A typical storyboard which was used to prepare and support the animations. Text is blurred on purpose.

The following clip (2:14 min) from the documentary introduces the viewer to the millions of Hawk-Eye data points that were analyzed for the documentary, and how the data was used to identify trends and patterns in Nishikori’s game.

The video then goes on to compare Nishikori’s hit point location from his 2012 and his 2014 US Open matches against Cilic. One of Nishikori’s strengths under Chang is that he plays ‘up’ on the baseline, taking time away from his opponent. In 2012 before Chang, Nishikori played only 34% of shots 1 m either side of the baseline. We refer to this zone as the attacking zone. In 2014 against Cilic again at the US Open, Nishikori played 49% of his shots in the attacking zone.

Finally we graph Nishikori and Wawrinka’s shot speed trend at the 2014 US Open. Nishikori’s shot speed trended constantly upwards throughout the entire match, while Wawrinka’s trended downwards. This was a distinguishing feature of Nishikori’s game at the US Open.

The complete documentary can be viewed here.

The analysis of the Hawk-Eye data provided ‘scientific’ proof of Nishikori’s strengths and weaknesses. It was also clear during the analysis and cross validating the results against player interviews that the players and coaches don’t always have a clear understanding of why they won or lost a match. We were able to validate the many assumptions, or commentary about a match with the use of such data.

The producer’s primary goal was to tell a story that was backed by real data. The animations played a critical part in delivering the story and messaging. They allowed us to simplify the 1 million plus data points that were analyzed, crunched, and spat out. Unfortunately there is only 43 minutes of tape in the final cut, but there were many revealing patterns and trends identified that are no doubt valuable to tennis players, coaches and sports reporters. If you would like to know more please get in touch. But for now, as they say in show business – that’s a wrap!

Video’s copyright NHK. Analysis and images copyright GameSetMap. Do not share the contents of this webpage without permission.

GameSetMap

Rethinking analytics for tennis using Hawk-Eye data.

Tag Archives: Kei Nishikori

Shot charts in tennis.

Kei Nishikori. Hawk-Eye Analysis Part 2

Kei Nishikori – Hawk Eye Analysis