Hawk-Eye Review, a system that was initially developed as a replay system for TV Broadcast coverage, has now become an important part of professional tennis. This ‘brave’ change to the sport’s rules has been welcomed by the vast majority of tennis players but especially spectators and TV viewers.

This innovative new method was pushed by some unfair results caused by bad calls and the demand for better ‘justice’. The 2004 US Open Quarterfinal between Serena Williams and Jenifer Capriati was the match that acted as the catalyst to introduce the hawk-eye review into a tennis tour event, the 2006 Nasdaq-100 Open.



Since then, Hawk-eye review has become part of tennis and players’ games. It can have both negative and positive affects on their game. Apart from winning or losing a point they can lose confidence, but also a winning challenge up on screen can help generate some good momentum or even a momentum switch. 

But how and when do players choose to challenge a call? Is this just a talent, instant reaction, good stroke feeling, good vision or a strategic behaviour and part of the game plan?

- If it is a player who only chooses to challenge a call when he feels he is 100% right, then this is a situation where a player can get really upset if the challenge is proved wrong and start questioning the electronic system itself.

The Hawk-Eye technology was used in the 2007 Dubai Tennis Championships with some minor controversies. Defending champion Rafael Nadal accused the system of incorrectly declaring an out ball to be in following his exit. The umpire had called a ball out; when Mikhail Youzhny challenged the decision, Hawk-Eye said it was in. Youzhny said afterwards that he himself thought the mark may have been wide but then offered that this kind of technology error could easily have been made by linesmen and umpires. Nadal could only shrug, saying that had this system been on clay, the mark would have clearly shown Hawk Eye to be wrong.

Additionally, during the finals of Federer against Rafael Nadal, Nadal challenged a shot which was called out. Hawk-Eye "proved" it otherwise (the call); not Nadal's challenge), with the ball just clipping the line. The reversal agitated Federer enough for him to request (unsuccessfully) that the umpire turn off the Hawk-Eye technology for the remainder of the match.

- A player who chooses to challenge a call when the call is very close and wants to take his chances against linesmen’s judgment. - This type of player will challenge a call when the ball is close but more likely a correct call, either in hope or to seek his chances against the credibility of the hawk-eye system. 

- Some players will choose to challenge a call when they have no chance to win it, but will use the few seconds of the review to compose themselves and therefore use this extra time for their own favour. If he has a couple more challenges left, this would also help.

- Sometimes players make really bad challenges with balls that are way out which can reveal the bad psychology he has at that moment. This will be picked up by the opponent and give him encouragement.

- There are times spectators play a big part in players’ momentum. Players can really get a psychological boost from hawk-eye proving the chair umpire wrong, as this is something crowds love and generally support the player who wins a challenge over the chair umpire.

- There are times when a player knows a call is wrong and his opponent will win the challenge and get upset with the chair umpire for not over ruling and creating an atmosphere where the crowd cheers for his opponent. For this reason some players choose to accept a call as their loss and not go through the electronic checking. (Novak Djokovic uses to do this some times)

- Finally there are times when a bad call will swap a good chance from the opponents’ second serve, back to a first serve. This one really hurts especially on break points.

The only surface hawk-eye review is not used is on clay courts. And that is because of the mark a tennis ball leaves on clay, so players can call up anytime the chair umpire to check the mark.

The only surface hawk-eye review is not used is on clay courts. And that is because of the mark a tennis ball leaves on clay, so players can call the chair umpire to check the mark. There are times though this is not enough…and there is a recent example in the Monte Carlo Masters last week when Djokovic is challenging 2 linesman’s calls and asks the chair umpire to have a look…well see what happens in the following video. The chair umpire does not change the call, but the electronic replay shows he is on both occasions wrong and Djokovic is right! Maybe it is time to use Hawk-eye on clay too! 

However, one thing proves right and not accidental; the fact  that Djokovic has got the best percentage when it comes to challenging calls which require the Hawkeye video replay system.

Here’s the percentage ranking in terms of video challenges among ATP World Tour players:

1. Djokovic, Novak (SRB) 92-76 55%
2. Davydenko, Nikolay (RUS) 58-72 45%
3. Nalbandian, David (ARG) 42-58 42%
4. Ginepri, Robby (USA) 30-45 40%
5. Federer, Roger (SUI) 122-192 39%
6. Ferrer, David (ESP) 39-60 39%
7. Ljubicic, Ivan (CRO) 35-54 39%
8. Fish, Mardy (USA) 34-54 39%
9. Nadal, Rafael (ESP) 85-152 36%
10. Safin, Marat (RUS) 72-139 34%

Last: Andy Murray: 25%