SAN DIEGO — The U.S. Open, San Diego style, brought morning fog that clung to the cliffs and spilled over to Torrey Pines Golf Course when Tiger Woods showed up for another nine-hole session today.

The setting could not have been more appropriate.

What once had been such a clear picture of this U.S. Open is now shrouded with uncertainty, starting with the left knee of the No. 1 player in the world. Woods has not played a competitive round since his runner-up finish at the Masters on April 13, having surgery two days later to clean out cartilage.

Perhaps even more startling was that Woods has not walked 18 holes since that Sunday at Augusta National — and most likely won't until he steps to the first tee Thursday morning.

"Is it fully recovered?" he said. "Probably not."

Woods played 17 holes last Wednesday in a cart, then retreated to his club in southern California for more cart golf over the weekend. Then came nine holes at Torrey on Sunday, Monday and Tuesday, and he typically doesn't play at all the day before a major begins.

It is not the ideal way to prepare for a major, and Woods has that down to a science. What helps is that he has owned Torrey Pines as much as any other golf course in the world, winning the Buick Invitational for the sixth time in January, by a tournament-record eight shots.

That made him an overwhelming favorite for the U.S. Open — but that was before knee surgery.

"It's difficult to take the amount of time he took off and come to a U.S. Open and dominate the way he has," Jim Furyk said. "That being said, nothing he does surprises me."

Sergio Garcia, among those expected to contend this week, said that didn't make him any less of a favorite.

"It's like Big Brown, with a crack (in the hoof)," Garcia said. "He was still the favorite."

Someone reminded Garcia that Big Brown failed to win the Triple Crown, finishing last among nine horses at the Belmont Stakes.

"Still a top 10," Garcia quipped.

Cameras flashed in the fog when Woods teed off, and thousands of spectators followed him along the back nine of the South Course, looking for a limp or the slightest sign of a game that would not be able to stand the rigors of 72 holes of golf's toughest test. That's assuming, of course, that Woods makes it all 72 holes.

The last time he played the U.S. Open after such a long layoff was two years ago at Winged Foot, when he returned from nine weeks off to deal with his father's death. He shots rounds of 76-76 and missed the cut for the only time in a major.

That was mental. This was physical.

In both cases, only the patient knows what's going on. And typical of Woods, he hasn't been forthcoming with information.

Has there been a shot that caused a twinge during practice, anything that caused him concern?

"It's a little sore," Woods said, "but not anything I haven't dealt with before."

Nothing looked out of the ordinary in the two hours it took him to play nine holes with Bubba Watson and Jordan Cox, an amateur from Stanford. If there was one moment to watch, it came on the par-5 13th that has stretched to 614 yards, a tee so far back from the course that Woods said, "We're almost in the ocean."

It can no longer be reached in two, so Woods split the middle of the fairway with his driver and hit an iron to lay up. But his second shot stopped on the down slope of the first cut of rough, leaving him about 130 yards from an awkward stance. All the weight is on the left side at address, and he took a hard swing to get the shot up in the air and over the bunkers to the elevated green.

That didn't look like much effort, certainly not much pain.

He would have liked to play Memorial to know for certain how he was hitting the ball and where it was going, that apparently was not an option. Woods said he wasn't even sure he could play the U.S. Open until two weeks ago.

"The week prior to Memorial, I was not feeling good enough where I was 100 percent sure I could play all four days," he said. "But then, my leg started getting a lot better quickly, which was great. My lifting went way up. My endurance came back. All the different things started coming up."

Someone asked him to put a percentage on how his knee felt.

"It's feeling better," was all he said, tiring of the questions.

If he learned anything from Winged Foot, it was that he could not ease his way into the round. Woods was battling for par from the opening hole and never quite recovered, slowly falling so far back that he was eliminated from the weekend.

What surely will get his attention Thursday is having Phil Mickelson next to him on the tee, joined by Adam Scott, the first time the USGA has grouped the top three players from the world ranking.

"The guy loves a challenge," swing coach Hank Haney said as he followed along. "And he loves this pairing with Mickelson. This will get him into the game quickly."

That is Woods' biggest concern — finding a rhythm that comes only from tournament golf, and finding it quickly.

Uncertainly also comes in the setup of the South Course, beyond the different conditions Woods, Mickelson and everyone else sees in the winter at the Buick Invitational. There could be four holes with vastly different tees, none more intriguing than the 14th hole. It plays 435 yards, but the USGA likely will play a forward tee from 277 yards for the final round.

The par-3 third will either be 195 yards or 142 yards, the difference between a middle iron and a wedge.

The scores? They could be anything.

"It's going to be a great test," Woods said. "The way they have set it up with different tees, different lengths, it can play so many different ways that it's going to be very interesting to see how the scores turn out."

One score in particular usually gets a lot of interest, especially this week.