Rory McIlroy let slip a two-shot lead and lost in a play-off at the Honda Classic in Florida while world number one Tiger Woods withdrew injured.
Northern Ireland's McIlroy, who carded a four-over-par 74, missed a 12-foot eagle putt at the last to win outright.
American Russell Henley won a play-off, which also featured compatriot Ryan Palmer and Scotland's Russell Knox, with a birdie at the first extra hole.
Woods was forced to withdraw on the 13th hole because of back pain.
The American hit a five-under-par 65 on Saturday to move into contention but was five over in his final round when he quit.
His withdrawal comes six weeks before the Masters at Augusta - the first major of 2014 - which takes place from 10-13 April.
"It's my lower back with spasms," said Woods, 38. "It started while I was warming up."
McIlroy admitted he was fortunate to have reached the play-off after dropping six shots in 11 holes from the seventh, including a double-bogey six on the par-four 16th where he hit his ball out of a bunker and into water.
He followed that with another bogey on the 17th, which left him needing a birdie on the last to get into the play-off at eight under.
The 24-year-old gave himself a chance of victory though with a stunning second shot on the par-five hole that finished 12 feet from the hole but he was unable to hole the eagle putt that would have won him the title.
"I didn't play well enough to deserve to win," McIlroy told the PGA tour website.
"It's very disappointing. It was a perfect opportunity to win. No one was really coming at me.
"There's a few positives to take, but obviously it's going to be hard to get over because I had a great chance to win my first tournament of the season and I didn't."
Henley, who qualified for the Masters, won at the first extra hole with a two-foot birdie putt.
"I was so nervous coming down the stretch," said Henley, who won his first PGA Tour title at last year's Sony Open in Hawaii.
"I hope I can have a bunch more Sundays just like that in my career. It was a rush to be out there playing with Rory and the crowd.
"I've never been part of a crowd so big cheering for me. It was an amazing feeling. It was so much fun."