Stan Wawrinka of Switzerland reacts after winning a point during a semifinal match against Kei Nishikori of Japan (not pictured) during the Rogers Cup tennis tournament at Aviva Centre in Toronto, Canada, July 31, 2016. [Photo/Agencies]

RIO DE JANEIRO - World number four Stan Wawrinka became the second high profile Swiss tennis player to quit the Rio Olympic Games, the Swiss Tennis Federation announced on Tuesday.

Wawrinka dropped out of the Games which open on Friday with a back injury after 17-time Grand Slam winner Roger Federer withdrew with a knee injury last Tuesday and announced he would not play again in 2016.

Double Grand Slam winner Wawrinka won a gold medal in men's doubles with Federer at Beijing 2008 Olympic Games.

In singles, Wawrinka reached the second round at Beijing 2008 and lost in the first round at London 2012 Olympic Games.