Former World No 1 Roger Federer has pulled out of next week's Montreal Masters, organisers said on Friday.
Federer, who recently said he was experiencing back trouble, did not give a reason for his withdrawal from the first big tournament of the north American hardcourt swing.
"I am disappointed not to be playing in Montreal next week. It is a great tournament with amazing fans. I look forward to competing there in the future," twice former champion Federer was quoted as saying on the event website.
The Swiss, who turns 32 next week, has suffered surprise defeats in his last three tournaments.
Beaten by the 116th-ranked Sergiy Stakhovsky in the second round at Wimbledon, the 17-time Grand Slam champion also lost to Federico Delbonis in the Hamburg semi-finals and 55th-ranked Daniel Brands on home soil in Gstaad.
Federer, who has slipped out of the world's top four for the first time since 2003, has won just one title this season, on Halle's grass in the build-up to Wimbledon.
Image: Roger Federer
Photograph: Thomas Lovelock/Getty Images