The world's number one tennis player Roger Federer returns the ball back from Germany's Tommy Haas during the semi finals of the Men's Dubai Tennis Championships on March 2, 2007. Federer won

Download this stock image: The world's number one tennis player Roger Federer returns the ball back from Germany's Tommy Haas during the semi finals of the Men's Dubai Tennis Championships on March 2, 2007. Federer won the match 6-4 7-5 and will play Russia's Mikhail Youzhny in the finals tomorrow. (UPI Photo/Norbert Schiller) - TXP6HF from Alamy's library of millions of high resolution stock photos, illustrations and vectors.

Germany's Tommy Haas returns the ball during his semifinal tennis match against Switzerland's Roger Federer at the ATP Gerry Weber Open tornament in Halle, Westphalia, Germany, Saturday, June 15, 2013. (AP Photo/Martin

Germany's Tommy Haas returns the ball during his semifinal tennis match against Switzerland's Roger Federer at the ATP Gerry Weber Open tornament in Halle, Westphalia, Germany, Saturday, June 15, 2013. (AP Photo/Martin

2006 federer hi-res stock photography and images - Alamy

Haas Defeats Federer To Win Halle Title (German)

Federer hammers Haas - Eurosport

Federer hammers Haas - Eurosport

Haas stuns Federer to win Halle title - Deseret News

Germany's Tommy Haas returns the ball during his semifinal tennis match against Switzerland's Roger Federer at the ATP Gerry Weber Open tornament in Halle, Westphalia, Germany, Saturday, June 15, 2013. (AP Photo/Martin

Photos: 'Dinosaurs' Roger Federer, Tommy Haas play doubles together - Sports Illustrated

Germany's Tommy Haas returns the ball during his semifinal tennis match against Switzerland's Roger Federer at the ATP Gerry Weber Open tornament in Halle, Westphalia, Germany, Saturday, June 15, 2013. (AP Photo/Martin