Jacob Bridgeman held off Rory McIlroy to claim his maiden PGA Tour victory at The Genesis Invitational as the American won by just one shot having led by seven earlier in the final round.
Bridgeman made the only two birdies of his final round in his first three holes to extend the six-shot lead he began Sunday with by one, but the 26-year-old stumbled his way to the finish line with three bogeys giving the chasing pack a chance.
McIlroy, playing alongside Bridgeman in the final pairing at Riviera Country Club, missed a series of makeable putts on the front nine but finally ignited his challenge by holing a stunning bunker shot at the 12th, before two birdies to finish left the Northern Irishman just one stroke back.
McIlroy's 67 meant he shared second with Kurt Kitayama, who produced a superb seven-under-par final round of 64 but was unable to make a closing birdie that would have drawn him level with Bridgeman.
Bridgeman hit two fine shots to leave what appeared to be a simple two-putt up the hill from 20 feet on the final green, but left the first one a few feet short, leaving himself to knock in a nervy three-footer to seal victory.
"I thought it was going to be a lot easier than that," Bridgeman said. "It was honestly easy until I got to about 16, and then it got really hard. I can't believe it. I made it about as hard as I could have made it I think at the end - making it one shot and having to make a three-footer, but this is incredible.
"I didn't really feel crazy nervous until I had a five-footer for bogey on 16, that one was sketchy. I hit a really good putt and luckily it went in, and then I was really nervous from there on out.
"I couldn't even feel my hands on the last couple greens. I just hit the putt hoping it would get somewhere near the hole, and both of them I left a mile short. I'm glad it's done now."
Adam Scott claimed the lowest round of the day with a 63 to claim fourth on 16-under, while South African Aldrich Potgieter was a shot further back in fifth.
American Jake Knapp was alone on 13-under in sixth, while Xander Schauffele, Tommy Fleetwood and last week's Pebble Beach winner Collin Morikawa were in a group tied for seventh on 12-under.
World No 1 Scottie Scheffler finished the tournament strongly with a 65 but saw his record streak of top-10 finishes on the PGA Tour end at 18 as he closed the week in a tie for 12th on 11-under.
McIlroy was left rueing his worst round of the week on Saturday, a 69, which ultimately left him with too much to do.
"I tried to make some things happen," McIlroy said. "I holed some putts on the back nine, which is nice, but I'll rue basically all 18 holes yesterday and then the front nine today, like 27 holes where I failed to capitalise on the chances I gave myself."
There were a couple of stunning moments at Riviera on Sunday, with England's Fleetwood holing out for eagle from 173 yards at the 15th, moments before Max Greyserman made a hole-in-one at the par-three 14th.
Before the PGA Tour action resumes, there's TGL action live on Your Site Golf each night from Monday to Wednesday, with the first indoor action coming at 10pm on Monday night when Atlanta Drive GC take on Boston Common Golf.
Then the PGA Tour moves on from California to Florida for the Cognizant Classic in The Palm Beaches at the PGA National Champion Course. Jacob Bridgeman is scheduled to be straight back in action, while notable names on the entry list include Brooks Koepka as he continues his PGA Tour return, and Ireland's Shane Lowry.
There's early coverage live on Thursday from 11.45pm on Your Site Golf ahead of full coverage from 4pm. or
