Serena Williams of the U.S. celebrates after winning against Czech Republic's Petra Kvitova in their WTA Qatar Ladies Open tennis quarterfinal match in Doha, Qatar, Friday, Feb. 15, 2013. (AP Photo/Osama Faisal)

Photo by: Osama Faisal

Serena Williams of the U.S. celebrates after winning against Czech Republic's Petra Kvitova in their WTA Qatar Ladies Open tennis quarterfinal match in Doha, Qatar, Friday, Feb. 15, 2013. (AP Photo/Osama Faisal)