Rookie Adam Long has sunk a 14-foot birdie putt on the final hole to win the Desert Classic for his first PGA Tour title.
Making just his sixth career start on the tour, Long closed with a seven-under 65 on the Stadium Course at PGA West to beat playing partners Phil Mickelson and Adam Hadwin by a stroke.
"I got a pretty good read off Phil's putt," Long said.
"It was one of those putts that you just stand over you just know you're going to make.
"And you can't control that, but when you have that feeling it's a good one.
"I'm in pretty disbelief right now. I don't really know what happened."
Long finished at 26-under par while Hadwin shot 67 and Mickelson, the leader after each of the first three rounds, carded a final round 69.
"I had a terrible putting day – one of the worst I can recall in a while," Mickelson said.
The 48-year-old Mickelson was making his first tour start since early October and first competitive appearance since he beat Tiger Woods in Las Vegas in November in a made-for-TV event.
Long set up with his winning putt with a six-iron from 175 yards with the ball below his feet in dormant grass on a mound to the right of the fairway.
The 31-year-old earned his PGA Tour card with a 13th-place finish last year on the Web.com Tour's regular-season money list.
Talor Gooch was fourth at 24 under after a 64, and Dominic Bozzelli followed at 22 under after a 66.
Last year's champion Jon Rahm shot 67 to finish sixth at 21 under.
Top-ranked Justin Rose closed with a 70 to tie for 34th at 14 under. He's the first No.1 player to play the tournament since the world rankings began in 1986.
Aaron Baddeley finished with a 65 to be the best-placed Australian at 16 under and a tie for 18th.
Cameron Davis (69) shared 28th a shot behind his compatriot while Curtis Luck struggled with a 75 to slide dow to seven under and tied 70th.