Nor was it the brace he wore as protection.

It was the fact that he couldn't sign autographs.

The most fan-friendly player in the game waved off fan requests in order to protect the wrist he hurt in a practice round at Oakmont on Memorial Day weekend.

"I have concerns," Mickelson said. "But I'm going to do the best I can do."

Mickelson, 36, appeared at peak form winning The Players Championship in May. It was his second victory this season, strong signs he was rebounding from his collapse at the 72nd hole of last year's U.S. Open. Mickelson was leading at Winged Foot but made double bogey at the final hole after bouncing his tee shot off a hospitality tent and slamming his recovery attempt off a tree.

Mickelson said two doctors have examined his wrist and concur there's inflammation but no serious damage. He has received cortisone shots and extensive therapy, but said he probably wouldn't play if it weren't the U.S. Open.

"It's certainly not the way I wanted to come into this tournament," said Mickelson, who's No. 2 in the Official World Golf Ranking behind Tiger Woods and is seeking his fourth major championship. "I haven't been physically able to practice as hard as I would like."

Mickelson has been hitting shots at the range and working on his short game, but today marked the first time he has played tee to green since withdrawing from the Memorial on May 31.