Lee Westwood withdrew from the WGC-Bridgestone Invitational and next week's USPGA Championship on Friday night.
And the world number three even hinted his participation in the Ryder Cup in October could be in doubt due to the ruptured plantaris muscle in his right calf.
"I will be out for as long as it takes to get right," Westwood told reporters after a second round of 76 left him seven over par at Firestone. "Hopefully it will be in time for the Ryder Cup."
Westwood suffered the injury at the end of June but still managed to finish a distant second behind stablemate Louis Oosthuizen in the Open at St Andrews.
However, the 37-year-old added: "It just seems to be getting worse. There's no strength in it.
"I don't have a deal of confidence in it, and then on the way down I'm finding it hard to hold my weight on it and then push off."
Asked what he could do to get better, Westwood added: "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 and I can't put any weight on it in the gym, so my legs feel weak. That's just it."
Six weeks out would leave Westwood with around two weeks to get ready for the Ryder Cup at Celtic Manor, which starts on October 1.