(CNN) -- Bill Haas should have spent Sunday celebrating a friend's wedding. Instead he was toasting a fourth PGA Tour title after beating major champions Phil Mickelson and Keegan Bradley in a playoff to clinch the Northern Trust Open.
Haas, the 2011 FedEx Cup series victor, looked to have won the California tournament outright after shooting two-under-par 69 in his final round.
But the new world No. 12 was pegged back after Mickelson, who was looking to secure back-to-back tour wins, and 2011 PGA Championship winner Bradley both birdied the par-four 18th to join him on seven under.
Haas eventually sealed victory with a 45-foot putt on the second additional hole, having earlier overhauled a two-stroke deficit on third-round leaders Mickelson and Bradley.
"I'm sure I'll talk to him later and hopefully his day is even better than mine," the 29-year-old Haas told the PGA Tour's official website when asked about missing friend Jon Hopson's big day. "It's pretty sweet for both of us today.
"I never expected to make a 40-footer, especially in that situation. A little luck was involved. I guess it was meant to be."
It wasn't just Haas who was surprised to see his effort find the cup, with both Mickelson and Bradley expecting him to come up short.
"Bill hit a tremendous putt," the 41-year-old Mickelson said. "We're thinking it's a very difficult three. It's a defensive hole. You're just trying to make four, believe it or not."
The 25-year-old Bradley added: "I didn't think he was going to make that one. I should have known, though, because he's a great putter and a great player."
The victory means has Haas won a PGA Tour title three years in a row, and moved him up to fifth in the early-season FedEx Cup standings.
Haas was battling a partisan crowd at the Riviera Country Club, with onlookers lending their backing to California native Mickelson -- a two-time winner of the event who was on a roll after clinching the AT&T National Pro-Am seven days before.
"Honestly 'Phil' sounds really similar to 'Bill,' so you just kind of pretend that maybe they're for you," said Haas. "If I'm at home, I'm cheering for Phil."
Former world No. 2 Sergio Garcia carded a stunning 64 to finish tied for fourth on five under, level with 10th-ranked Dustin Johnson (71), his fellow American Jimmy Walker (69) and New Zealand's Jarrod Lyle (70).
American trio Bo van Pelt (70), J.B. Holmes (70) -- who is back this year after brain surgery -- and Jonathan Byrd (73) were tied for eighth on four under.
Australian world No. 8 Adam Scott (70) was part of a seven-way tie for 17th which also included 2007 Masters champion Zach Johnson (72) and last month's Farmers Insurance Open winner Brandt Snedeker (70).
British world No. 1 Luke Donald endured a torrid final round and carded eight bogeys on his way to a 78 which saw him finish seven over.