World number three Paul Casey today withdrew from the US PGA Championship due to a rib injury, tournament organisers said.
The Englishman, a three-time winner this year, had strained an intercostal muscle preparing for last month's Open Championship at Turnberry and was forced to withdraw from last week's WGC-Bridgestone Invitational in Ohio after just six holes of his opening round.
Casey received treatment on the injury on a daily basis and played nine practice holes at Hazeltine National in Minnesota on Wednesday.
He arrived at the course this morning, however, and did not feel fit enough to make his 7.45am (1.45pm BST) tee time alongside Japan's Hiroyuki Fujita and Nick Watney of the United States.
Casey's place will be taken by Tim Petrovic.
Casey said: "I'm very disappointed but I have to look at the bigger picture which is the fact that I will play a lot more majors over my career and I have to be ready for what is coming up the rest of the season with the FedEx Cup and The Race to Dubai.
"But it is very frustrating because standing there hitting easy golf swings it is not that bad. It is just starting to pull when you are getting to six irons and longer.
"If it is doing that on a flat lie on the range, then I can't risk it on the golf course.
"It seems like there has been a lot of guys who have had similar issues in the past and the advice I have been given from the experts and a lot of the players is don't push it too quickly."
Casey said he had given himself every chance to compete.
"I feel good that I tried everything to try and get it ready and I also gave Tim Petrovic an hour. He was out there warming up alongside me so I went to speak to him myself and told him to go and play well."