* Gay edges out Howell and Lingmerth in sudden-death
* Earns fourth PGA Tour win with birdie at second extra hole (Adds Gay quotes, further detail)
By Mark Lamport-Stokes
LA QUINTA, California, Jan 20 (Reuters) - Brian Gay clinched his fourth PGA Tour title in champion style when he beat fellow American Charles Howell III and Swede David Lingmerth in a sudden-death playoff to win the Humana Challenge on Sunday.
Gay, 41, sealed victory in fading light on the Palmer Private course at PGA West after striking a superb approach to five feet at the par-four 10th, the second extra hole, and coolly sinking the birdie putt.
Howell, bidding to claim his first title on the U.S. circuit in six years, bogeyed the hole after ending up in the back left bunker in two, splashing out to nine feet beyond the pin and missing the par putt.
PGA Tour rookie Lingmerth was eliminated at the first extra hole, the par-five 18th, where he bogeyed after hitting his second shot into water. Howell, with a solid two-putt, and Gay, who chipped to four feet, both birdied the hole.
"It feels amazing," Gay told reporters after securing the winner's cheque for $1.008 million and a two-year exemption on the PGA Tour. "I'm still in a little bit of shock. It kind of happened so fast there at the end the way things went down."
The trio had finished the 72 regulation holes on 25-under-par 263, Howell signing off with an eight-under 64, Gay carding a 63 and Lingmerth matching the day's best score with a 62.
American Scott Stallings, five strokes in front overnight, bogeyed the par-five last after hitting his second shot into water to drop out of the lead for the first time in the final round, finishing with a 70 in a tie for fourth at 24 under.
"There weren't any nerves or anything like that going into it," Stallings said about his wayward six-iron approach at the 18th. "Just hit a bad shot.
"Felt like I made a good swing, just the ball ... got a bad kick and went in the water. But it is what it is."
Stallings had been in control of the tournament after firing a 63 in Saturday's third round and he maintained his five-shot lead with three birdies in his first four holes, narrowly missing an eagle putt from nine feet at the par-five second.
However, he faltered at the seventh with a three-putt bogey, his par putt from inside two feet catching the left edge of the cup and spinning away for his lead to be cut to two strokes.
Stallings then failed to take advantage of the driveable par-four eighth, chipping from greenside rough to three feet before again lipping out.
After parring the ninth to reach the turn in two-under 34 with a one-shot cushion, he birdied the 10th and 11th to stay a stroke in front of the chasing Gay.
Though Stallings scrambled well to save par from a greenside bunker at the 12th and also at the par-five 14th, where he drove into a canal, he bogeyed 16 to drop back into a tie for the lead with Gay, Lingmerth and Howell.
After safely parring the 17th, Stallings struck a perfect drive down the 18th fairway but then stunningly pulled his approach into the lake guarding the left side of the hole, winding up with a bogey to finish a stroke outside the playoff.
"I knew Scott was five ahead and even with a really low round, it would be tough to catch him, if at all," Gay, long regarded as one of the best putters on the PGA Tour, said of the task facing him at the start of the day.
"I played great on the front, just tried to stay aggressive and shoot low."
Twice former champion Phil Mickelson, making his first appearance on the 2013 PGA Tour, signed off with a seven-birdie 66 to share 37th place at 17 under, having recovered well from a rusty 72 in the opening round.
"I feel like I'm starting to play well, hit some putts on line," said the four-times major champion, who had been battling flu-like symptoms earlier in the week.
"So hopefully I'll be able to make a run on the weekend here next week, because that's what's exciting, is having a chance to win," Mickelson added, referring to the Jan. 24-27 Farmers Insurance Open. (Reporting by Mark Lamport-Stokes; Editing by Patrick Johnston)