Rio Olympics 2016: Venus Williams upset in first round

Venus Williams will have to lean on her younger sister if she wants to add another Olympic medal after she was beaten by Kirsten Flipkens on Saturday.

The United States stalwart was upset 4-6 6-3 7-6 (7-5) by Belgium's Flipkens in the first round of the Rio Games, a disappointing showing for the number five seed in what will surely be her final Olympics.

Flipkens collapsed on the green hardcourt in elation after winning the third-set tie-break, exhausted after a match that lasted three hours, 13 minutes.

The decisive breaker came moments after the Belgian was broken to love by Williams when she had a chance to serve out the match.

Williams, 36, won the singles gold medal 16 years ago in Sydney and has doubles gold medals with sister Serena from 2000, 2008 and 2012.

The Williams sisters are the top seed in the Rio doubles tournament and are in first-round action on Sunday.