Rory McIlroy may be forced to pull out of the US PGA in Atlanta after he suffered a wrist injury during the first round.
The Northern Irishman, who claimed the US Open in June, struck a tree root on the third hole and is expected to make a decision about his fitness before his second round.
Despite the injury, McIrloy managed to card an even par 70 in his opening round, which leaves him seven shots of the lead held by Steve Stricker.
"It was just like a sharp pain up the forearm and there's a little bit of swelling just on the inside of my wrist," the 22-year-old said.
"Then it was going up into my elbow and my shoulder. It's throbbing a bit and every time I went through a shot I was in a lot of pain."
The US Open holder received lengthy treatment on course and will wait as long as possible before making a decision on whether or not he will continue.
Tiger Woods continued his comeback from injury with a seven-over round of 77.