The Czech Republic's Lucie Safarova and Barbora Strycova may have offered the biggest upset of the Olympics so far this summer when they knocked out Venus and Serena Williams in the first round of the women's Olympic doubles 6-3, 6-4.

The American sisters had previously won the event three times – 2000, 2008 and 2012 – and had never lost a doubles match over the course of a run of 15 Olympic games, yet fell out of this year's competition at the very first hurdle.

Questions had been raised of 36-year-old Venus, who had been knocked out of the women's singles the day before by Kirsten Flipkens after suffering from a virus that had limited her performance on the night.

"We played terrible, and it showed in the results," admitted Serena after the match. "I wasn't playing the way I need to play, I wasn't crossing the way I need to cross."

Going in to the Rio Games as No.1 seed, the Williams sisters have won eight gold medals for the United States over the course of their careers and came in to the competition having won their 14th Grand Slam championship together.

“I wouldn’t say it’s devastating,” Serena later added. “We had a chance to compete for our country and we did the best that we can. We had a blast out there. It was a lot of fun and we’ll always remember these moments and these matches, and I think that’s what matters most.

“We’ve had so many Olympic doubles golds, so many grand slam championships. It’s been unbelievable.”

Neither Safarova nor Strycova had ever won an Olympic doubles match and were unseeded for the Rio competition. Furthermore, Strycova was in fact a late replacement for Safarova's initial partner, Karolina Pliskova, who had withdrew before the tournament.