World number one Roger Federer has pulled out of next week's Madrid Masters after injuring his right ankle ligaments in training, organisers said on Wednesday.
"Federer has phoned today to tell me that he suffered an injury while trying to hit a drive," tournament director Manolo Santana said on the event's website.
"He has a strong injury in his right ankle, so he won't play in Madrid. He is walking on crutches."
Federer's doctors said the Wimbledon and US Open champion is also expected to pull out of the following week's ATP tournament in his home city of Basel, an event he has yet to win.
Federer missed last year's Madrid Masters because of fatigue. He also missed the Basel event last year after rupturing a thigh muscle on the tournament's opening day.
His doctors said the Swiss might also be ruled out of the Paris Masters, which starts on October 31, but could be fit to defend the season-ending Masters Cup event in Shanghai.
(Additional reporting by Mark Ledsom in Switzerland)