But his coach reckons Tiger will be able to tee it up on a course he loves.

"I think he'll play," said Harmon. "But I don't know how well."

Woods sustained the injury stepping on the ankle of an overzealous fan coming off the 18th green.

Woods was swarmed by autograph seekers as he left the 18th green, walking briskly and trying to sign whatever programs and hats where thrust in front of him.

One man, who had been hounding him for autographs during his practice round, tried to position himself in front of the pack, and Woods' inadvertently stepped on his ankle, hyperextending his knee.

"A lot of fans just ... came down on top of me," Woods said. "One guy ran in front. I stepped on his ankle, and my weight going forward and his weight coming back ... I hyperextended my knee."

Woods winced immediately, glowered at the man and grabbed the back of his leg as he hobbled up a hill. He tried to hit balls after lunch, but couldn't.

"People get aggressive. That's the way it is," Woods said. "That's one reason we have security.

"Some of you say, 'Why do you have so much security?' It's for instances like this, so they don't happen. Unfortunately, it happened today."

Woods said the physical therapists in the fitness trailer told him he had sprained a ligament in his knee.

Woods won both tournaments staged on the Monterey Links course last year, following up his win in the AT&T Pro Am with an easy victory in the US Open.

The 25-year-old has never withdrawn from an event since joining the US Tour five years ago.