Potter was unflappable playing alongside Johnson, who next week completes one full year at No. 1 in the world. That changed when he tapped in for par on the 18th hole, and he choked back emotion of a week he won't soon forget.
He stepped off a curb in Canada in August 2014 and broke his ankle, keeping him out of golf for two years and then back to the minor leagues a year ago. Potter's only other victory was at The Greenbrier Classic in 2012. He has missed the cut in 55 percent of his PGA Tour events in his career.
And then he didn't flinch next to Johnson, with Mickelson making a late charge and Day never too far behind.
"It's been a struggle," he said. "You break your ankle and you don't know what's going to happen with your swing, with your career. It's unbelievable right now. ... This has been a blast this week."
Potter, who came into the week at No. 246 in the world, earns a trip back to the Masters for the first time in five years. He finished at 17-under 270 and earned $1,332,000, nearly half of his career earnings going into the week.
It was another disappointment for Johnson (right) going into the final round. He now won five out of 12 times when he took at least a share of the 54-hole lead into the final round. Johnson led briefly when Potter three-putted for bogey on the opening hole. That didn't last long, and the tone of the final round was set along the ocean holes on the front nine.
Johnson lost a good birdie chance when his flip wedge found a bunker on No. 4. He hit his worst shot of the week on the tee at No. 5, which sailed right and over the cliff and forced him to make a good up-and-down to escape with bogey.
Both were just over the back of the seventh green. Johnson played a low chip and grazed the cup. Potter played a more lofted shot that dropped for birdie. Johnson went over the eighth green and into the bunker, leading to another bogey and never got any closer.
"A few iron shots cost me a few bogeys," said Johnson, who played Pebble in 70-72 on the weekend. "Two under in 36 holes is not too good as well as I thought I was playing. I'd like to have put a little more pressure on Ted."
Mickelson (left) began his move late with three birdies in a four-hole stretch ended at the par-3 17th. Needing an eagle to have any chance, his approach to the 18th was a few yards short and found a bunker. He failed to get up and down.
Reavie, a playoff loser in Phoenix last week, went out in 31 and was at 15 under, two shots behind. He made eight pars and a bogey on the back nine, with most of the damage coming on a wedge that came up short and into the bunker on the par-5 14th. With back-to-back runner-up finishes, Reavie goes to No. 43 in the world.
Day ran out of steam after missing the 17th on the wrong side of the green. He at least kept it entertaining on the 18th when he tried to hit driver off the deck and hooked it over the sea wall. He found his ball along a patch of sand and pebbles and played from the beach, over the wall, over the green and into a bunker. He saved par with a 15-foot putt.
Potter now has a two-year exemption on the PGA Tour, along with getting spots in the Masters and PGA Championship.
Mickelson had his highest finish since he was runner-up to Henrik Stenson in the 2016 British Open at Royal Troon. Coming off a tie for fifth at the Phoenix Open, this is the first time he has put together consecutive top 5s since he won back-to-back in 2013 at the Scottish Open and British Open.
The other tournament also was a runaway. Arizona Cardinals receiver Larry Fitzgerald teamed with Kevin Streelman to win the pro-am portion of the event by seven shots.