Serena Williams of the USA serves to Samantha Stosur

Serena Williams of the USA serves to Samantha Stosur of Australia in their round four match at the Australian Open tennis tournament in Melbourne, Australia

Serena Williams of the United States returns to Victoria Azarenka of Belarus during their Women's singles quarterfinal match at the Australian Open tennis championship in Melbourne, Australia.

Venus Williams of the United States reacts after losing a point to Li Na of China during their Women's singles quarterfinal match at the Australian Open tennis championship in Melbourne, Australia