...his 4th round US Open match against Croatian Marin Cilic at the USTA Billie Jean King National Tennis Center September 8, 2009 in New York. TOPSHOTS/AFP PHOTO/TIMOTHY A. CLARY (Photo credit should read...

...Belgium during their semifinal match of the 2009 US Open at the USTA Billie Jean King National Tennis Center, in New York, September 12, 2009. AFP PHOTO/Stan Honda (Photo credit should read STAN HONDA...

...forehand in his match against Olivier Rochus of Belgium during Day One of the Davidoff Swiss Indoors Tennis at St Jakobshalle on November 2, 2009 in Basel, Switzerland. (Photo by Julian Finney/Getty Images

US Fed cup player Alexa Glatch (top) celebrates with her teammates victory over Czech republic's Iveta Benesova during the second semifinal match of F...

US Fed cup players Liezel Huber (L) and Bethanie Mattel-Sands (R) celebrate their Victory over Czech couple Iveta Benesova (top) and Kveta Peske (not ...

Serena Williams of the US returns to her sister Venus during their WTA Championships final tennis match at the Khalifa International Tennis and Squash Complex in Doha on November 1, 2009. Serena Williams...

...NOVEMBER 01: Roger Federer of Switzerland talks to the media during previews for the Davidoff Swiss Indoors Tennis at St Jakobshalle on November 1, 2009 in Basel, Switzerland. (Photo by Julian Finney/Getty Images

...United States after winning the singles final against Venus Williams of the United States at the WTA Tennis Championships, in Doha, Qatar Sunday, Nov. 1, 2009

...Williams of the USA in their round robin match during the Sony Ericsson Championships at the Khalifa Tennis and Squash Complex on October 28, 2009 in Doha, Qatar

...eyes the ball before returning it to Denmark's Caroline Wozniacki during their WTA Championships semi-final tennis match at the Khalifa International Tennis and Squash Complex in Doha on October 31, 2009. AFP PHOTO...

...hits a ball to Svetlana Kuznetsova of Russia (out of camera range) during their WTA Tour Championships tennis match in Doha on October 29, 2009. AFP PHOTO/STR (Photo credit should read STR/AFP/Getty...

Andre Agassi competes in the Lipton tennis tournament in 1994

Dinara Safina of Russia serves shortly before retiring from her singles tennis match against Serbia's Jelena Jankovic on the second day of the 4.55 million dollar WTA...

...of the United States in their round robin match during the Sony Ericsson Championships at the Khalifa Tennis and Squash Complex on October 28, 2009 in Doha, Qatar

US tennis champion Serena Williams returns the ball to her sister Venus during their Maroon Group match on the...