Wawrinka, 30, agreed to pose without clothes for an issue of ESPN The Magazine that goes on sale on July 10th.
But just as Wimbledon got under way this week the sports network published a couple of photos online, which drew immediate attention from Swiss media on Tuesday.
The snaps, taken for the magazine’s The Body Issue, show a naked Wawrinka swinging a racket on an indoor court.
“My body is for my tennis, it’s for my sport,” Wawrinka told ESPN.com.
“I’m not a model at all,” the six feet (183-centimetre) tall Lausanne native said.
“I don’t work out to go to the beach, I work out to play well and to do well on the court.”
There’s little sign of excess flab on Wawrinka’s physique but he told ESPN that he was “a little bit fat" at the age of 13 or 14.
“I wasn’t like big-time fat, I was just overweight,” he said.
“At the time I wasn’t practising that much, tennis was just a hobby. But it wasn’t easy to feel that way.”
The Blick newspaper said Wawrinka’s decision to pose in the buff was a sign of his new confidence after winning at Roland Garros last month.
He was one of 24 athletes to pose in their birthday suits for the magazine.
Last year, tennis stars Venus Williams and Tomas Berdych stripped for the publication’s 2014 Body Issue.