That turned out to be Phil Mickelson, not Tiger Woods.
In a big, big way.
Mickelson went from a six-shot deficit to a two-shot lead in just six holes, closed with an 8-under 64 for a two-shot victory over Charlie Wi and gave Woods a Sunday thrashing not many saw coming.
Mickelson and Woods played in the second-to-last group, and Mickelson beat him by 11 shots. He won for the fourth time at Pebble Beach, and became only the ninth player in PGA Tour history with 40 wins.
"Pebble Beach ... it feels awesome no matter what number it is," Mickelson said.
It was anything but that for Woods, who was reduced to a supporting role on a cool, overcast day along the Pacific. Right when it looked as though Woods might still be in the game after holing a bunker shot for birdie on the par-3 12th, Mickelson answered by pouring in a 30-foot par putt.
Mickelson seized control for good with a 40-foot par save on the 15th hole, and he played it safe — Mickelson is capable of that every once in a while — on the 18th hole and still made birdie.
Wi, who started the final round with a three-shot lead, four-putted for double bogey on the opening hole and never quite recovered. He closed with back-to-back birdies for an even-par 72 and his fifth runner-up finish on tour.
It was the third straight week on tour that the winner started the final round at least six shots behind a 54-hole leader going after his first tour victory.
The shocker, though, was how Woods fell apart.
He has been taking big strides with his game over the past few months, and he looked poised to break through after a 67 in the third round at Pebble Beach got him to within four shots of the lead.
But he failed to make birdie on the easy opening stretch at Pebble Beach, and even when he made his first birdie at the par-5 sixth, Mickelson poured in a 20-foot eagle putt to take the outright lead.
"I didn't hit it as bad as the score indicated, but I putted awful," Woods said. "As good as I felt on the greens yesterday, I felt bad today. Anything I tried to do wasn't working. Consequently, I made a ton of mistakes on the green."
Two weeks ago in his 2012 debut at Abu Dhabi, Woods was tied for the lead with unheralded Robert Rock going into the final round and didn't break par, tying for third.
Woods used to own Mickelson, but that changed at the 2007 Deutsche Bank Championship. This was the fifth straight time Mickelson posted the better score when playing in the same group as Woods in the final round.
Mickelson has won three of those tournaments, although they have yet to be in the final group on those occasions.
Mickelson started his season sluggishly, failing to crack the top 25 at the Humana Challenge and Phoenix Open, and missing the cut at Torrey Pines. He said his putting was as good as ever, and it was a matter of getting his game in sync.
It simply sang on Sunday, mostly his amazing touch on the greens — a long eagle putt at No. 2 that caught part of the hole, long two-putts for par and enough birdies to make him a winner at Pebble Beach again.
"It feels just amazing," Mickelson said. "I felt like my game was there, but coming out the first couple of weeks, I posted some horrendous scores and started to question it. To be able to play the way I did the last 18 holes really means a lot."
Mickelson finished at 17-under 269 and earned $1.152 million for his first win since the Houston Open last year. He will move to No. 11 in the world.
Ricky Barnes closed with a 67 and finished third. Kevin Na tied for fifth and earned a spot in the Match Play Championship in two weeks at Arizona.
Wi talked about battling the demons of self-doubt, and they must have had the first green surrounded. Equipped with a three-shot lead to start the final round, Wi four-putted from 35 feet above the hole for a double bogey.
Just like that, the game was on.
That still wasn't enough for Woods to get in on the action. Standing in the sixth fairway, Woods was only one shot out of the lead, yet the sleeves of his red shirt and his name on the leaderboard didn't seem to make him stand out the way it has before.
The opening holes had something to do with that, and watching Mickelson play alongside him.
Mickelson nearly holed an eagle putt across the second green; Woods missed a 5-foot birdie putt that stayed 2 inches above the hole. Mickelson holed a 15-foot birdie putt down the hill at the fourth; Woods had a 30-foot putt up the hill that was 3 feet short. Mickelson's tee shot on the par-3 fifth settled a foot from the cup. Woods missed his birdie putt from 12 feet.
Yes, there was a big charge at Pebble Beach — from Lefty.
Mickelson started the day six shots behind and went two shots ahead with an eagle on the sixth hole. Woods then vanished in a series of blunders — missing a 2½-foot par putt on the seventh, missed a 5-foot par putt on the eighth, and a third straight bogey at No. 9 when he hit his approach into the bunker.
The only hope for Woods came on the 12th, when he holed his bunker shot. It looked like it might be a two-shot swing, pulling him to within three of the lead, until Mickelson made his 30-footer for par.
On the next hole, Mickelson hit an approach to 2 feet and Woods' tee shot landed in a divot.
''It's frustrating because I had a chance," Woods said. "All I had to do was get off to a good, solid start. And I didn't do that."