San Diego ? Tiger Woods is entering the unknown.

We’re entering the unknown with him. Golf aficionados are split in their opinions of how the world’s best golfer will do at the 108th U.S. Open at Torrey Pines.

The tournament starts today, and it will be the first time since April 13 that Woods has played 18 competitive holes.

“I haven’t played in a while,” Woods said. “I haven’t played competitively since the Masters. So getting out there and getting into the flow and dealing with the adrenaline… I’m really excited about getting out there and feeling that.”

The rest of us aren’t as excited as we are eager. Jack Nicklaus was the best the baby boomer generation saw. Woods is our Nicklaus.

He has done things with a golf club and ball that seem to defy logic – the chip shot on 16 at Augusta in 2005; the shot in 2000 at Glen Abbey, from the fairway bunker about 220 yards out, over water; the 9-iron he hit 155 yards for the hole-in-one at TPC Scottsdale in 1997; and the list could continue.

Now the question is whether Woods’ surgically repaired left knee can hold up through four days of 18 holes?

Woods had a stoic look when he was told of people saying he just can’t do it, that he can’t overcome his knees and be what many of us are accustomed to him being, what many expect him to be.

“I’ve heard that before,” he said, with a low laughter filling the room. “I’ve heard that before.”

It’s difficult for me to doubt Woods. Hurt or not, physically, he’s the best I’ve ever seen swing a club. Mentally, he might be the best athlete I’ve ever seen.

A hurt Woods only hit 14 greens in regulation the last time he played 18. A hurt Woods won the Bridgestone Invitational and PGA Championship in consecutive weeks. A hurt Woods only embarked on the longest winning streak of his career.

The last time Woods returned from surgery, he won three of his first four events.

The last time he returned from a long layoff was after the death of his father. Woods missed the cut in the 2006 U.S. Open, the only time he has missed a cut in a major.

But Torrey Pines is different. Woods loves this course. It has been kind to him, too. He won the Buick Invitational here in January. Woods has won the past four times he has played at Torrey Pines.

“You know, I think that he has come back from injury and won the first week back in the past,” said world No. 2 Phil Mickelson, who will play with Woods and No. 3 Adam Scott the first two rounds. “He has had huge layoffs and come back and won. He takes a bunch of time off before his tournament in L.A., and he comes out and he wins.

“I just don’t see how it’s going to have a negative effect on him. I just can’t see a better player make adjustments easier than Tiger. I just don’t think it will be a problem.”

Coming up No. 18 on Tuesday, Woods hit a 100-yard shot that landed about six feet from the hole. The ball slowly rolled, picked up speed and rolled off the green and into a pond.

The crowd groaned.

Woods’ caddie tossed another ball. Woods, not hesitating, took another swing.

This time the ball landed pin high and rolled to within 2 feet of the cup.

Maybe Woods isn’t entering the unknown after all.