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RIO DE JANEIRO, BRAZIL - AUGUST 07: Juan Martin Del Potro of Argentina celebrates after victory against Novak Djokovic of Serbia in their singles match on Day 2 of the Rio 2016 Olympic Games at the Olympic Tennis Centre on August 7, 2016 in Rio de Janeiro, Brazil. (Photo by Clive Brunskill/Getty Images)

RIO DE JANEIRO, BRAZIL - AUGUST 07:  Juan Martin Del Potro of Argentina celebrates after victory  against Novak Djokovic of Serbia in their singles match on Day 2 of the Rio 2016 Olympic Games at the Olympic Tennis Centre on August 7, 2016 in Rio de Janeiro, Brazil.  (Photo by Clive Brunskill/Getty Images)