Lee Westwood will not play in next week's final Major of the season, the USPGA Championship, after pulling out of the WGC-Bridgestone Invitational with a swollen right calf.
The world number three is also a doubt for October's Ryder Cup, although the Englishman is still optimistic that enough rest will mean he's able to tee up at Celtic Manor.
"I will be out for as long as it takes to get better," Westwood said after carding a six-over-par 76 in the second round at Firestone Country Club.
"I am just hoping that it will be in time for me to play in the Ryder Cup."
Westwood, who had a chance to grab the world number one spot this week as Tiger Woods continues to struggle with his game, has not been fully fit for some time.
He ruptured the plantaris muscle in his right calf at the French Open but somehow managed to play in the Open at St Andrews, where he finished second behind Louis Oosthuizen.
"It just seems to be getting worse," added the Englishman.
"There's no strength in [the leg]. I don't have a deal of confidence in it, and then on the way down [in his swing] I'm finding it hard to hold my weight on it and then push off."
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