Westwood says he needs a break from playing to resolve his injury problem
Lee Westwood has pulled out of the WGC-Bridgestone Invitational and next week's USPGA Championship because of a badly swollen right calf.
The British world number three has been hampered by the injury since before the start of last month's French Open.
"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 has played in six consecutive editions of the biennial Europe v United States event, which takes place this year at Celtic Manor in Wales from 1-3 October.
He ruptured the plantaris muscle in his right calf at the French Open but managed to be fit enough to play in the Open at St Andrews, where he finished a distant but creditable second behind Louis Oosthuizen.
Westwood, 37, went into the World Golf Championship series tournament in Ohio with a chance of supplanting Tiger Woods as world number one.
He shot a one over par first-round 71 in Ohio to be seven shots off leader Bubba Watson, and his 76 on Friday left him well out of contention.
Afterwards he said of his injury: "It just seems to be getting worse.
"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."
Asked what else he could do to aid his ankle's recovery, he replied: "Sit on my backside for six weeks like they keep telling me.
"It's the only way to improve it. I'd like to be working out but I can't put any weight on it in the gym, so my legs feel weak."
The USPGA Championship tees off on Thursday 12 August, at Whistling Straits in Kohler, Wisconsin.