It’s his worst first round in a major.  One hour after he started, Tiger Woods was atop the leaderboard Thursday at the PGA Championship and felt like the Tiger of old. He never imagined he would finish with his worst score ever in the opening round of a major.

He opened with three birdies in five holes. He followed with three double bogeys over the next 10 holes.

Woods started out with his name high on the board, right next to Steve Stricker, who went on to tie a major championship record with 63. Woods wound up toward the bottom, next to John Daly and 57-year-old Jerry Pate, with a 77.

It was his worst round in a major since Woods shot an 81 in the vicious wind and pelting rain of Muirfield in the third round of the British Open nine years ago. And it was no mystery to him how it all happened.

“Got off to a great start today, was three under early, was having mechanical thoughts through those holes … and I thought, ‘I can let it go’ and play by instinct and feel,” he said. “And it just screwed up my whole round. I’m not at that point where I can do that yet.”

Woods returned to competition last week and completed his first tournament since the Masters, staying away from golf until he was certain that injuries to his left leg would no longer cause him trouble.

The head — not to mention his swing — still have plenty of work.

Woods looked serious as ever when he walked onto the putting green to begin warming up. Then came an 18-foot birdie putt on the opening hole, an aggressive five-wood from a blind shot in the pine straw on the par-five 12th, followed by a bunker shot from a plugged lie to 3 feet for another birdie.

He hammered a drive more than 300 yards in the air on the 14th, leaving him a wedge to 3 feet for another birdie.

“He’s back!” a fan cried out. Not quite.

It was the worst opening round for Woods in any tournament since he shot 79 at the Australian Open in 1996. He is due to play Down Under again in November. At this rate, that might be his next tournament. If he misses the cut today — he has done that only twice in the majors — he would not be eligible for any PGA Tour events for six weeks.

Not since the final round at Bay Hill in 2007 had Woods made at least three double bogeys in one round. He started this carnage with a four-iron on the 254-yard 15th hole that didn’t look awful until it landed, just to the right of the green and into the pond.

Woods was in the sand a dozen times.

He has talked about returning to his old swing while trying to learn a new one, and he said that was the case Thursday.

“And that’s what’s frustrating,” Woods said. “I thought I was playing well enough that I don’t have to do that. I can just go out there and play and let it go and just play by feel — see the shot, hit the shot, feel it. And I’m not at that point yet. My same motor patterns get in there. I start fighting it, and I couldn’t get it back.”

WATERLOGGED: At least Woods fared better than Japanese teen Ryo Ishikawa, thought to be a contender coming off a strong showing last week in the WGC-Bridgestone Invitational at Firestone.

The 19-year-old should’ve brought his swimsuit, putting six balls in the water and finishing with an 15-over 85 — pretty much assured of missing the cut before much of the field even got on the course. It got so bad at one point that Ishikawa said he “stopped counting.”

His goal for the second round? “Birdies on every hole, all 18,” he said.