The Williams sisters' perfect run at the Olympics is over.
Venus and Serena Williams suffered their first-ever 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.
MORE: Photos from the Rio '16 Olympic opening ceremony
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 seed and were favored to play deep into the tournament. But Venus' first-round singles loss to Kirsten Flipkens on Saturday — a match that lasted more than three hours — didn't bode well for the sisters, and they fell in an early hole Sunday.
After taking the first set, the Czechs picked up a key break of Venus to go up 3-2 early in the second, but the Americans immediately broke back to get level. But Safarova and Strycova again pounced on Venus in her next service game, breaking 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.