The Australian Open

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Rafael Nadal of Spain celebrates after defeating 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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Andy Murray of Britain bites on his shirt during his fourth round match against Stephane Robert of France at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Rick Rycroft)

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

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Jelena Jankovic of Serbia makes a backhand return to Simona Halep of Romania during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Rick Rycroft)

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Simona Halep of Romania disputes a point during her fourth round match against Jelena Jankovic of Serbia at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 20, 2014.(AP Photo/Rick Rycroft)

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