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MELBOURNE, AUSTRALIA - JANUARY 24: Novak Djokovic of Serbia prepares to receive serve in his fourth round match against Gilles Simon of France during day seven of the 2016 Australian Open at Melbourne Park on January 24, 2016 in Melbourne, Australia. (Photo by Scott Barbour/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 24:  Novak Djokovic of Serbia prepares to receive serve in his fourth round match against Gilles Simon of France during day seven of the 2016 Australian Open at Melbourne Park on January 24, 2016 in Melbourne, Australia.  (Photo by Scott Barbour/Getty Images)