Venus and Serena Williams had never lost an Olympic doubles match before Sunday, but Lucie Safarova and Barbora Strycova ended that run.
Venus and Serena suffered their first loss in doubles at the Olympics on Sunday, upset 6-3, 6-4 by the Czech duo of Lucie Safarova and Barbora Strycova in the first round in Rio.
The American legends had won gold in 2000, 2008 and 2012; they did not participate in the 2004 Athens Olympics.
Though slowed a bit by age, they entered Rio as the top seeds and were favoured to play deep into the tournament. However, Venus' first-round singles loss to Kirsten Flipkens on Saturday - a match that lasted more than three hours - did not bode well for the siblings, and they fell in an early hole on Sunday.
After taking the first set, the Czechs picked up a key break of Venus to go 3-2 up early in the second, but the Americans immediately broke back to get level.
Safarova and Strycova again pounced on Venus in her next service game, though, breaking to earn the chance to serve for the match.
This time, Strycova was able to consolidate the break and serve it out, with a mis-hit return by Venus sealing a massive upset for the unseeded Czechs.