The Australian Open

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Novak Djokovic of Serbia makes a forehand return to Leonardo Mayer of Argentina during their second round match at the Australian Open tennis championship in Melbourne, Australia, Wednesday, Jan. 15, 2014.(AP Photo/Aaron Favila)

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Novak Djokovic of Serbia signs autographs after winning his second round match against Leonardo Mayer of Argentina at the Australian Open tennis championship in Melbourne, Australia, Wednesday, Jan. 15, 2014.(AP Photo/Aaron Favila)

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Novak Djokovic of Serbia waves to the crowd after winning his second round match against Leonardo Mayer of Argentina at the Australian Open tennis championship in Melbourne, Australia, Wednesday, Jan. 15, 2014.(AP Photo/Aaron Favila)