Swiss tennis player Stan Wawrinka has pulled out of the Olympic Games due to a back problem.
The world number four, a two-time grand slam winner, was diagnosed with "local overstress" after experiencing pain during the Rogers Cup in Canada last week.
The 31-year-old has now joined countryman Roger Federer, the world number three, in withdrawing from Rio 2016, where the tennis competition is set to get underway on Saturday.
"After a medical examination by his doctor in Geneva, the current world number four has to withdraw from the Olympic Games which will start in Rio de Janeiro later this week," the Swiss Tennis Federation said in a statement.
Wawrinka added: "I'm very sad.
"I was really excited about playing in Rio. After Beijing and London I was very much looking forward to playing in my third Olympic Games. I wish all the Swiss athletes the best of luck throughout the coming weeks."
Wawrinka and Federer, who will not play again this season, won men's doubles gold in China in 2008.
Belinda Bencic, the Swiss women's number two and world number 16, has also been forced out of the Olympics due to concerns over a wrist injury.