Justin Thomas chips onto the 18th green during the first playoff hole Sunday at the Sentry Tournament of Champions in Kapalua, Hawaii. / AP photo by Matt York

KAPALUA, Hawaii — Justin Thomas won the Sentry Tournament of Champions, though he still doesn't know how.

He lost a two-shot lead with three holes to go in regulation, had to play the par-5 18th hole four times Sunday and always seemed to be scrambling just to stay in the game in a three-man playoff.

In the end, there was more exhaustion than elation.

"I really don't know how I won today," Thomas said. "I got very fortunate."

The thrill-a-minute start to the calendar year on the PGA Tour ended with Thomas chopping his way to bogey on the 18th, getting another chance when Xander Schauffele three-putted for par on the final hole in regulation to force a playoff and then twice having to watch Patrick Reed stand over a putt to win.

On the third playoff hole — the last one before darkness would have suspended competition on Maui — Thomas recovered from another poor shot with a sand-wedge shot that illustrates why his short game is among the best in golf. He played a high cut from 113 yards that landed just over the ridge with enough spin to settle three feet away from the hole for a birdie putt.

His caddie, Jimmy Johnson, had asked if it was safer to put the ball in the air or pitch it low and ride the slope. Thomas replied: "I need to make birdie. I'm not worried what the safest play is. We need to make 4."

Reed, who never had the lead all day, had a 30-foot eagle putt and a 12-foot birdie putt in the playoff to win. His last chance was an eight-foot birdie with Thomas in tight, and it was too strong. Making the finish even uglier was a fan who screamed "Cheater!" after he hit the putt. Reed turned and glared.

It was a reference to his rules violation at the Hero World Challenge in the Bahamas last month, when video showed him scooping away sand to improve his lie. Reed was penalized two shots for it, and he faced extreme heckling by the Australian crowd the following week at the Presidents Cup.

"It stings at the end whenever you don't birdie for the win," said Reed, whose closing 7-under-par 66 matched the best score of the tournament. "But really, I gave myself an opportunity. I put myself in position to have a chance, and I needed a little bit of help at the end there, and they gave it to me, allowing me to even get in the playoff."

Thomas, who closed with a 69 after bogeys on two of his last three holes, won for the third time in his past six starts on the PGA Tour. It was his 12th career victory, one more than Jordan Spieth and the most of any active player younger than 30.

Thomas hit a terrible tee shot in regulation, and the 3-wood shot that followed didn't carry through the knee-high vegetation. He took a penalty drop, hit a wedge shot to put the ball eight feet away from the cup and missed the par putt.

Schauffele, who closed with a 70, hit the green in two shots — only the seventh time that happened all week on the rain-softend conditions of the Plantation Course at Kapalua Resort — and had 35 feet for eagle. The 30 mph gusts helped to send his first putt seven feet by the hole, and he missed the birdie try in his bid to become the first player in 10 years to win back-to-back at this event.

Schauffele was eliminated after the first extra hole when he three-putted from 100 feet away at the front of the green, leaving his first putt 20 feet short.

"I should have won the tournament," said Schauffele, who at No. 9 in the World Golf Ranking is five spots behind Thomas and three ahead of Reed. "J.T. was right there. But under the circumstances, I should have closed it out. I did everything I was supposed to until the last moment."

Reed was never tied for the lead until nearly an hour after he made a 20-foot birdie putt on the final hole. That put him at 14-under 278, which looked as though it would not be good enough.

Thomas had a two-shot lead when he swirled in a three-foot birdie putt on the 15th hole, and then he came undone. His tee shot on the 16th hole found a bunker, and then he missed an eight-foot par putt. Thomas holed a six-foot putt for par on the next hole, lightly pumping his fist because he kept a one-shot lead with the par-5 18th remaining.

"I botched it up pretty badly," Thomas said.

For a moment, the 26-year-old former University of Alabama standout and 2017 PGA Championship winner thought he had wasted one of the best rounds he had ever played. He ran off six birdies in eight holes to turn a two-shot deficit into a two-shot lead, an astounding display given the strength of the wind.

"That stretch of holes J.T. went through, I'd like to see anyone else try it," Schauffele said. "He was hitting ridiculous shots, making good putts in the wind and he deserved the lead he got."

Ultimately, Thomas got the victory that took longer than he might have expected.

The playoff participants finished regulation three clear of the rest of the 34-man field, with Patrick Cantlay (68) fourth and Rickie Fowler (69) and rising star Joaquin Niemann (70) of Chile tied for fifth at 10 under. Another stroke back in seventh were Dustin Johnson (71), Collin Morikawa (71) and Gary Woodland (72).

Spain's Jon Rahm (72) — who at No. 3 was the highest-ranked player at the event limited to winners from last year — finished 10th at 8 under.

Chattanooga native Keith Mitchell, the former Baylor School and University of Georgia golfer whose PGA Tour breakthrough came last March at the Honda Classic, closed with an 81 and tied for 32nd. Mitchell, who turns 28 on Tuesday, opened with a 76 at Kapalua and had his most success in the middle rounds, with a 72 on Friday and a 73 on Saturday.

The PGA Tour remains in Hawaii this week, moving to Oahu and Waialae Country Club for the Sony Open, which starts Thursday. Thomas shot a 59 and set several scoring records on the way to his victory at the 2017 edition.

Then it's back to the mainland for the West Coast swing before the first World Golf Championship of the year next month in Mexico City.