Novak Djokovic shocked by 'tough' Olympics defeat to Juan Martin Del Potro

Novak Djokovic admitted his shock first round defeat to Juan Martin Del Potro was "one of the toughest losses in my life" as his hopes of claiming an elusive Olympic gold in the men's singles went up in smoke in Rio.

Djokovic, who also lost to Del Potro in the bronze medal play-off at London 2012, had no answer to the power of the Argentinian, with the 2009 US Open champion sealing a 7-6 (7/4) 7-6 (7/2) victory in almost two and a half hours.