Rio 2016: Stan Wawrinka pulls out but Rafael Nadal will play at Olympics
Switzerland's world number four Stan Wawrinka has withdrawn from the Rio Olympics but Spaniard Rafael Nadal has confirmed he will compete.
Wawrinka, 31, aggravated a back injury during the Rogers Cup in Canada, meaning five of the men's top-10 players will not participate in Rio.
Roger Federer, Tomas Berdych, Milos Raonic and Dominic Thiem have also withdrawn.
Nadal has been suffering with a wrist injury but is fit enough to feature.
The 14-time Grand Slam winner, 30, has not played since the French Open in May but will compete in the singles, doubles and mixed doubles in Brazil.
Wawrinka suffered a shock second-round defeat at Wimbledon this year, losing to Argentine Juan Martin del Potro, who was ranked 165th in the world.
The injury is another blow for the Switzerland team after 34-year-old Federer, the world number three and 2012 silver medallist, withdrew with a knee injury.
That leaves just two remaining players - Martina Hingis, whose last appearance at the Games was in 1996, and Timea Bacsinszky - from the initial six-member Olympic team.
World number seven Raonic and world number eight Berdych cited the Zika virus for their pullouts.
British number one and 2012 gold medallist Andy Murray defended the withdrawals and claims it remains a "strong field".
"It's unfortunate with Roger and Stan," he said.
"They're two guys that are both great players and capable of winning events like this, so it's a shame that they aren't here."