Roberto Bautista Agut of Spain hits a backhand return to Grigor Dimitrov of Bulgaria during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aijaz Rahi)
Grigor Dimitrov of Bulgaria hits a backhand return to Roberto Bautista Agut of Spain during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aijaz Rahi)
Sloane Stephens of the U.S. serves to Victoria Azarenka of Belarus during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Eugene Hoshiko)
Victoria Azarenka of Belarus makes a backhand return to Sloane Stephens of the U.S. during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)
Dominika Cibulkova of Slovakia celebrates her win over Maria Sharapova of Russia during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)
Maria Sharapova of Russia reacts after losing a point to Dominika Cibulkova of Slovakia during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Eugene Hoshiko)