Rio 2016: Novak Djokovic in tears after losing to Juan Martin del Potro

World No 1 Novak Djokovic crashed out of the Olympic men's singles in the first round, losing in straight sets to Argentina's Juan Martin Del Potro in a defeat he called 'one of the toughest' of his life. 

Novak Djokovic, who also lost to Del Potro in the bronze medal play-off in London in 2012, had no answer to the power of the 2009 US Open champion, who sealed a 7-6, 7-6 victory in almost two and a half hours. 

The 27-year-old, who has dropped to 141st in the world after almost two years out with wrist problems, did not face a single break point on his serve and hammered 29 forehand winners past a helpless Djokovic. 

An Olympic gold medal is the biggest prize missing from Djokovic's trophy cabinet after he finally won the French Open in June, becoming the first man in 47 years to hold all four grand slam titles at once. 

Djokovic's winning grand slam run came to an end with a shock third-round loss to Sam Querrey at Wimbledon, but the 29-year-old had bounced back by claiming his 30th Masters title in Toronto last week and was a hot favourite in Rio. 

He was visibly emotional as he left the court in Rio after defeat, departing in tears following his surprise defeat to Del Potro.