Rafael Nadal of Spain looks at a blister on his hand during his fourth round match against Kei Nishikori of Japan at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014. (AP Photo/Aaron Favila)
Rafael Nadal of Spain gets up after he fell during his fourth round match against Kei Nishikori of Japan at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)
Victoria Azarenka of Belarus celebrates after defeating Sloane Stephens of the U.S. in their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)