Turns out that Tiger Woods was just along for the ride.
Mickelson closed with an 8-under 64, beating Woods by 11 shots in a one-sided showdown at the Pebble Beach National Pro-Am.
"I just feel very inspired when I play with him," said Mickelson, who has posted the better score the past five times he has played alongside Woods in the final round.
"I love playing with him, and he brings out some of my best golf. I hope that he continues to play better, and better, and I hope that he and I have a chance to play together more in the final rounds."
Woods, one shot out of the lead on the sixth hole after 54-hole leader Charlie Wi fell apart early, followed his first birdie of the final round with three straight bogeys, starting with a three-putt from 18 feet on the par-3 seventh.
It never got much better from there.
He finished a miserable day with another three-putt on the 18th for a 75, the only consolation coming from belief that he's closer than ever to putting it all together.
"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."
At least he got to watch a clinic.
Mickelson went from six shots behind to a two-shot lead on the par-5 sixth hole when he rolled in a 20-foot eagle putt, adjusting his read after watching Woods' amateur partner -- Dallas Cowboys quarterback Tony Romo -- miss from a similar line.
Woods holed a bunker shot for birdie on No. 12, but right when it looked like a two-shot swing that could give Woods some momentum, Mickelson made a 30-foot par putt. With Woods out of the way, Mickelson made a 40-foot par putt on the 15th hole to keep a three-shot cushion, and he was never challenged from there.
He wound up with a two-shot win over Wi, who four-putted for double bogey on the opening hole and never recovered.
Mickelson, who finished at 17-under 269, became only the ninth player in PGA Tour history with 40 career wins. This one was special for many reasons, and the thrashing he gave Woods was but a small part of it.
His wife, Amy, flew up for the weekend and gave him a pep talk Friday in the rain at Monterey Peninsula when Mickelson was going nowhere. He ran off five birdies, got back into the tournament and picked up a win he didn't see coming.
As much as Woods talks about his game being close, Mickelson felt the same way. His last win was the Houston Open last April, and while he thought he was putting well, his scores didn't reflect it.
"It's one of the more emotional victories for me than I've had, and the reason is I've had some doubt these last couple of weeks, given the scores I've shot," Mickelson said. "Having these great practice sessions, I started to wonder if I'm going to be able to bring it to the golf course. So this gives me a lot of confidence and erases the doubt."
The last shred of doubt came on the 14th, a diabolical green that turn birdies into bogeys without caution. Woods hit a wedge that went down the side of the green, requiring two chips to get on the green. He made bogey.
Mickelson's caddie, Jim "Bones" Mackay got in his hear.
"He erased all doubt and said, `Let's get aggressive and make birdie, we need one more here,"' Mickelson said. "It just got me aggressive and into a positive frame of mind."
He went at the flag and made birdie.
Wi, who started the final round with a three-shot lead, birdied his last two holes for a 72 and his fifth runner-up finish on tour. It was the third straight week that the winner began the final round at least six shots behind a 54-hole leader going for his first tour victory.
"I fought back and hung in there, because the four-putt on the first hole, I was really shook up pretty badly and my strokes were pretty iffy at best," Wi said. "I hung in there all day. My time will come."
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 needed a start like Mickelson, and was never really in the game.
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.
"What was frustrating is that I had a chance," he said. "All I had to do was get off to a good, solid start today. And I didn't do that."
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.
"Although I feel like he brings out the best in me, it's only been the past five years," Mickelson said. "Before, I got spanked pretty good. Let's not forget the big picture here. I've been beat up. But the last five years, I've been able to get some of my best golf out when we play together."
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.
Even with Wi falling apart, that 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.
"He played really good today," Woods said. "He was hitting it flush. And his wedge game was right on the money."