Denmark's Caroline Wozniacki slips on the grass during her first round women's singles match against Austria's Tamira Paszek. – Photo by AFP

Caroline Wozniacki of Denmark, right, congratulates Tamira Paszek of Austria after she lost their first round women's singles match. – Photo by AP

Serbia's Novak Djokovic serves during his second round men's singles victory over US player Ryan Harrison. – Photo by AFP

Novak Djokovic of Serbia slips during his men's singles tennis match against Ryan Harrison of the U.S. – Photo by Reuters

Covers on the outside courts during a rain shower on day three of the 2012 Wimbledon Championships tennis tournament. – Photo by AFP

Spectators sit under an umbrella as rain delays play between Samantha Stosur of Australia and Arantxa Rus of Netherlands. – AP Photo

Australia's Samantha Stosur shows her frustration during her second round women's singles defeat to Netherland's Arantxa Rus. – Photo by AFP

Arantxa Rus of the Netherlands hits a return to Samantha Stosur of Australia during their women's singles tennis match. – Photo by Reuters

Switzerland's Roger Federer plays a volley during his second round men's singles victory over Italy's Fabio Fognini. – Photo by AFP

Romania's Sorana Cirstea celebrates after winning the first set during her second round women's singles match against China's Li Na. – Photo by AFP

China's Li Na plays a shot during the loss in her second round women's singles match against Romania's Sorana Cirstea. – Photo by AFP

Maria Sharapova of Russia serves to Tsvetana Pironkova of Bulgaria during a second round women's singles match. – Photo by AP

Kim Clijsters of Belgium (R) acnknowledges Andrea Hlavackova of the Czech Republic after defeating her in their women's singles tennis match. – Photo by Reuters