* McDowell beats Simpson with par at first extra hole
* Seals victory when Simpson misses a six-foot putt
Graeme McDowell held his nerve in fierce winds to clinch his second PGA Tour title with a playoff victory over U.S. Open champion Webb Simpson at the RBC Heritage in Hilton Head Island, South Carolina on Sunday.
Northern Irishman McDowell sealed the win with a regulation two-putt par at the first extra hole, the 18th, where Simpson three-putted for bogey after missing the green to the right with his approach.
Using a putter for his third shot from 33 feet, Simpson narrowly missed the left edge of the cup with his birdie attempt, his ball ending up six feet beyond the hole after being blown by a sudden gust.
After former U.S. Open champion McDowell left his birdie putt from 13 feet inches short and right before tapping in for a four, Simpson missed his par putt and sank to his knees in anguish.
"I'm just disappointed for Webb," a gracious McDowell told CBS television in a greenside interview after emerging triumphant on a day when ocean winds gusted up to 40 mph (64.37 kph) across Harbour Town Golf Links.
"He hit a great first putt there on this playoff hole and he got a terrible gust of wind. That's kind of the way it was today. It was really tricky and gusty. I am just really happy to get my first official (regular) PGA Tour win across the line."
McDowell clinched his maiden PGA Tour victory at the 2010 U.S. Open, maintaining his composure in tough scoring conditions at a wind-buffeted Pebble Beach to end a 40-year title drought by Europeans in the year's second major.
"I played nicely, I played nicely all week," said the 33-year-old McDowell, a seven-times winner on the European Tour. "It's a great golf course here.
"I sat down with (2010 Heritage champion) Jim Furyk on Tuesday ... and he said, 'You're never out of this tournament. You've just got to hang around and hang around.'
"And I did that. I played great Friday. The putter was cold most of the week but I really got it going today."
The pair had finished the 72 regulation holes on nine-under-par 275, McDowell three-putting to bogey the last for a two-under 69 and Simpson closing with a 71.
English world number six Luke Donald, who made a sizzling start with four birdies in the first six holes, lost momentum after the turn on the way to a 69, finishing joint third at seven under with American Kevin Streelman (72).
Overnight leader Charley Hoffman limped home in five-over 40, a closing 77 dropping him back into a three-way tie for sixth at five under.
The final round was always going to be difficult as strong winds gusted through the tree-lined layout but Simpson made a fast start with two early birdies, a 10-footer at the par-four third putting him a tie for the lead with Hoffman at 11 under.
American Hoffman briefly dropped back with a bogey at the fourth, where he missed the green with his approach, but then benefited from a two-shot swing at the par-five fifth.
While Simpson bogeyed the hole after finding a fairway bunker off the tee and the right rough with his second shot, Hoffman rolled in a 12-foot birdie putt there to edge a stroke in front at 11 under.
As howling winds swept across the course, the long-haired Hoffman bogeyed the sixth after driving into trees but he reached the turn with a one-shot lead, Simpson having missed a six-foot par putt at the eighth.
Within the space of a few minutes early on the back nine, three players ended up in a tie at the top of the leaderboard.
McDowell, who had drained a 28-foot birdie putt at the 11th, coolly sank a 20-footer for par at the 13th to remain at nine under and bogey-free for the round.
Level with the Northern Irishman were Hoffman, who bogeyed the par-four 12th after finding a bunker with his approach and splashing out 16 feet beyond the hole, and Simpson, who sank a four-footer there for birdie.
Hoffman's title challenge effectively ended when he double-bogeyed the par-three 14th after dumping his tee shot into water before McDowell went ahead for the first time with his birdie at the 16th.
Though McDowell made his only bogey of the day at the par-four 18th, where he ran his approach putt from just off the back of the green 12 feet past the cup, he coolly clinched the title on the first extra hole.