The Australian Open

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Roger Federer of Switzerland puts off the shirt during a break in his fourth round match against Jo-Wilfried Tsonga of France at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)

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Roger Federer of Switzerland serves to Jo-Wilfried Tsonga of France during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aaron Favila)

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Roger Federer of Switzerland serves to Jo-Wilfried Tsonga of France during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Aijaz Rahi)

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Rafael Nadal of Spain celebrates after his win over Kei Nishikori of Japan during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Eugene Hoshiko)

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Maria Sharapova of Russia answers questions during a press conference following her fourth round loss to Dominika Cibulkova of Slovakia at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014. (AP Photo/Shuji Kajiyama Shuji)