Switzerland's Stan Wawrinka became the latest top-tier player to pull out of the Rio Olympics.
The world No. 4 cited a back injury that he sustained last week at the Rogers Cup, where he reached the semifinals.
"I am very sad because after Beijing and London I would have liked to experience my third Olympic Games in Brazil," Wawrinka said in a statement to the Swiss Tennis Federation on Tuesday. "Unfortunately that will now not be possible."
In 2008, Wawrinka won doubles gold with partner Roger Federer, beating the Swedish team of Simon Aspelin and Thomas Johansson in the final. But Wawrinka's singles ascent did not start until a few years later, when in 2014 he took down Novak Djokovic and Rafael Nadal en route to his first Grand Slam title at the Australian Open.
A year later, Wawrinka triumphed at Roland Garros, becoming the only current player outside the famed Big Four (Federer, Djokovic, Nadal and Andy Murray) to win multiple majors.
Wawrinka, 31, joins four other top 10 players, including Federer, as Rio withdrawals.