Will Wimbledon 2009 be a repeat of last years US Open final with Murray and Federer?

It’s Wimbledon fortnight, the unofficial start of the UK summer. There is real hope this year that through Andy Murray, the world number 3, the UK may get a home Wimbledon champion, the first since Fred Perry in 1936. Unfortunately for tennis fans reigning champion and world number one Rafael Nadal had to withdraw last week with a knee injury. With Nadal unable to defend his crown this year it gives the opportunity for Roger Federer to once again be the world number one. Fans will be looking forward to a final featuring both Murray and Federer and with so much for both men to play for, hopefully a final less one sided than the US open final last year that Federer dominated to win.

Professional tennis has recently begun to allow players to challenge the umpire’s calls by utilising a computer system called Hawk-eye. Hawk-eye visually tracks the path of the ball and displays a record of its actual path as a graphic image. The US Open in 2006 was the first Grand Slam tournament to use Hawk-eye allowing players to challenge line calls. As long as the player continues to challenge incorrect umpire calls, the player is allowed to continue making challenges.

Research recently published in the journal Current Biology, investigated how the position the moving tennis ball is perceived to have bounced depends on the direction the ball is travelling in. A perceptual error is often made by professional tennis umpires, which players could exploit to their advantage, with successful challenges having significant effects on the outcome of matches.

There are commonly two types of errors made by tennis umpires:

• ‘Predicted errors’ are those in which the umpire judges incorrectly that the ball’s bounce position was further forward in the direction of the balls travel. These errors are commonly when a ball bounces on the line and so in play, yet is called out.
• ‘Unpredicted errors’ are those incorrect judgements that the tennis ball moved in a direction opposite of the balls motion, these errors are often when a ball bouncing out of play is called in.

To measure whether umpires accurately perceive the position at which a tennis ball bounces, the researchers from the University of California randomly reviewed 4457 points from random 57 matches played during Wimbledon 2007. They reviewed and recorded each case in which a tennis ball landed close to or on a line. Of 83 erroneous calls 70 were classified as predicted errors by the researchers and only 13 were unpredicted. Of 85 players challenges that were called 25 calls were overturned, a umpire error rate of around 30%.  The researchers also looked at Wimbledon 2008 matches and found that of all the players’ challenges that got over turned, 69% were predicted errors.

Whilst players are likely to have the same misperception that the umpires have, they are likely to challenge too few predicted errors. The author Dr David Whitney, suggests that players should maximise their challenges because the referee error rate is high amongst close calls. But also players should predominantly challenge calls consistent with perceptual error for example they should concentrate their challenges on balls that are called ‘out’.

The skill of challenging umpire’s calls is now an essential part of the professional tennis game.  It  would be assumed  that both umpires and players are aware of research such as this but it will be interesting to watch this year’s Wimbledon to see if umpires still have a bias towards predicted errors, or with all the pressures and emotion on court if players restrain themselves to only challenge calls of ‘out’.