(Reuters) - Ted Potter, Jr. kept his cool as he outplayed some of the game’s biggest names to win the Pebble Beach Pro-Am by three shots in California on Sunday.

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Few gave Potter, ranked 246th in the world, a chance as he started the final round tied for the lead with world number one Dustin Johnson, and a bogey at the first seemed to suggest the stocky left-hander was destined to fall short.

But he stormed back with four birdies in the next six holes, punctuated by a 20-foot chip-in at the par-three seventh, to jump clear and was never overtaken thereafter as he posted a three-under-par 69 in fine conditions at Pebble Beach.

By parring the final 11 holes, he forced his closest pursuers to make something happen.

“I knew on the back nine I had a two-shot lead (and) ... if I played smart golf ... those guys would have to catch me coming in,” an emotional Potter said in a greenside interview.

Potter finished at 17-under 270 for his second PGA Tour win, after his previous success in 2012.

Overnight co-leader Johnson made four bogeys in his even-par 72 to blow his chances for an 18th PGA Tour title and ended tied for second with fellow Americans Phil Mickelson and Chez Reavie and Australian Jason Day on 14-under.

The victory was a remarkable comeback by Potter, who incurred a fractured right ankle in a “freak accident” in 2014 when he slipped on a path.

“I had the first surgery in 2014 and then I had another surgery in 2015 to have all the screws and plates removed,” he said.

“You don’t know what’s going to happen with your golf swing or your career. To come back from that it’s just unbelievable right now.

“It still gets sore at the end of the day, but I can swing the golf club and can I get around 18 holes, so I feel good about that.”

While Potter celebrated victory, joint runner-up Mickelson’s winless drought since the 2013 British Open continued, though he drew positives from three birdies in the final five holes for a 67.

“I gave it a shot on the back nine,” he said.

“It was nice to feel the nerves and make a couple of birdies coming down the stretch. Right now I’m hitting it as well as I have in a long time.”