Lee Westwood, the world's third-ranked player, withdrew after the second round of the Bridgestone Invitational Friday at Firestone Country Club.
A muscle tear in his right calf will also keep him out of the final major of the year, next week's PGA Championship at Whistling Straits.
Westwood has finished in the top three in four of the last five majors, dating back to a tie for third at last year's British Open. The Englishman also tied for third at the 2009 PGA, finished second in the 2010 Masters and second at the British Open, when he was also bothered with the injury. The problem first flared up at the Alstom Open de France July 1-4 in Paris.
''I will be out for as long as it takes to get better,'' Westwood said in a statement. ''I am just hoping that it will be in time for me to play in the Ryder Cup.''
The competition between the U.S. and Europe is slated for Oct. 1-3 at Celtic Manor Resort in Newport, South Wales. Westwood said on Friday before he left the course that the only way his leg would improve would be six weeks of rest.
"'It seems to be getting worse,'' Westwood said after Friday's round of 76 left him at 7-over par. ''I there's no strength in it. I don't have any confidence in it. Then on the way down (as he swings) I'm finding it hard to hold my weight on it and then push off.
'"It's unfortunate it's happened now when I'd like to be playing at my best. I can't even hit balls now. It's evident that I'm rusty since the (British) Open because I haven't been able to practice. It's just a vicious circle, really. I'd like to be working out, but I can't put any weight on it in the gym, so my legs feel heavy.''