World number one Novak Djokovic crashed out of the Olympic men’s singles in the first round on Sunday, losing in straight sets to Argentina’s Juan Martin Del Potro.
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 (7/4) 7-6 (7/2) 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 the Serbian’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.
Having added flag-waving to his list of talents, Andy Murray got back to the day job in thoroughly convincing fashion as he launched the defence of his Olympic title with victory over Viktor Troicki.
The London 2012 gold medallist was playing his first match since defeating Milos Raonic to win a second Wimbledon title a month ago but there were no signs of rust as he eased to a 6-3 6-2 victory.
The win was Murray’s 13th in a row and seventh at the Olympics, and he will look to extend the run when he faces Argentina’s Juan Monaco in the second round.
Elsewhere, defending champions Serena and Venus Williams suffered their first ever Olympic doubles loss in the opening round in Rio.
The sisters, who won gold medals in 2000, 2008 and 2012, were beaten 6-3 6-4 by Czech pair Barbora Strycova and Lucie Safarova in a big upset.
Venus finds herself out of the tournament after only two days, unless she decides to play mixed doubles, having lost to Kirsten Flipkens in the opening round of the singles on Saturday night.