Novak Djiokovic of Serbia in action against Juan Martin Del Potro of Argentina during their men’s singles first round match at the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS

Juan Martin Del Potro of Argentina in action against Novak Djiokovic of Serbia during their men’s singles first round match at the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS

Novak Djokovic of Serbia in action against Juan Martin Del Potro of Argentina during the men’s singles match of the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS

Juan Martin Del Potro of Argentina leans on the net after a point against Novak Djokovic of Serbia during the men’s singles match of the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS

Juan Martin Del Potro (R) of Argentina is congratulated by Novak Djokovic of Serbia after beating the World No. 1 during the men’s singles match of the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS

Novak Djokovic of Serbia waves as he leaves the court after losing against Juan Manuel del Potro of Argentina during the men’s singles match of the Rio 2016 Olympic Games Tennis events at the Olympic Tennis Centre in the Olympic Park in Rio de Janeiro, Brazil, 07 August 2016. EPA/MICHAEL REYNOLDS