KAPALUA, Hawaii — Patrick Reed never thought he had a serious chance to win at Kapalua until he stood over an 18-foot birdie putt in a playoff Monday.

Like so many other times in his young career, he didn’t waste it.

Four shots behind with four holes to play, Reed, a former University High golfer, made two birdies, holed an 80-yard shot for eagle and got just enough help from Jimmy Walker to win the Hyundai Tournament of Champions for his fourth career PGA Tour victory.

“I thought my chances were slim,” Reed said. “So I was just thinking to myself, ‘let’s try to birdie three of the last four and get ourselves a chance to secure second alone, and give ourselves a chance — just maybe.”

A two-putt birdie on the par-5 15th. The wedge he holed on the 16th for eagle. And after a three-putt from 100 feet just off the green at 17 slowed his momentum, Reed two-putted for birdie from 80 feet on the par-5 18th for a 6-under 67.

Then it was up to Walker, who appeared to have control until he tried to play it safe off the tee on the short par-4 14th and found a bunker, leading to his first bogey in 33 holes at Kapalua. Walker twice missed birdie putts inside 10 feet, and he missed an 18-foot birdie putt for the win in regulation.

He closed with a 69 to join Reed at 21-under 271.

In the playoff, Walker’s chip went over the green, and he had a 6-foot par putt that he never had to hit when Reed made his winning putt.

“It was there for me to win,” Walker said. “It was a bummer I didn’t close the door on it.”

The 24-year-old Reed joined some elite company as the fifth player in the last 25 years to win at least four times on the PGA Tour before turning 25. The others were Rory McIlroy, Sergio Garcia, Tiger Woods and Phil Mickelson.

“Everyone is trying to get to the best in the world,” Reed said. “But that’s going to take a long time. It’s nothing that happens overnight.”

The trick is to win, and Reed already has shown he has that knack with his fourth win in his last 35 starts on the PGA Tour. But it was his first victory since the World Golf Championship at Doral, where he caused a stir by saying he was among the top five players in the world.

This moved him to a career-best No. 14, though he was more interested in what he could do get better.

Jason Day became the second player on Monday to tie the Plantation Course record with a 62 — Chris Kirk shot 62 earlier in the day as the first player out. Day posted at 20-under 272, though that score never looked as though it would be enough. Russell Henley closed with five straight birdies for a 67 to join Day at 272.

They were joined by Hideki Matsuyama, tied with Walker at the start of the final round. The 22-year-old from Japan also felt as though he lost a good opportunity to win.

He missed birdie chances on the last four holes and missed them all to shoot 70.

Walker and Matsuyama were locked in a spirited duel over the front nine until Walker landed what appeared to be a knockout punch. He holed a 20-foot birdie putt on No. 8, hit a great fairway metal from a downhill lie onto the green at the par-5 ninth for a two-putt birdie, and then made a 10-foot putt at the 10th for his third straight birdie.

That gave him a three-shot lead over Matsuyama, and he kept that margin stepping to the 14th tee.

It all changed so quickly.

Walker ended his bogey-free streak when he tried to play conservatively off the tee at the 14th by hitting a 4-iron. It sailed right into a bunker, and he went over the green and missed a short par putt.

In the group ahead of him, Reed birdied the par-5 15th and suddenly took a share of the lead by holing a wedge from 80 yards out for eagle on the 16th hole.

“I walked to 17 tee and heard that Jimmy was at 21 (under) as well,” Reed said. “I was like, ‘Oh, wow.’”

Just like that, it was a sprint to the finish.

Reed looked as if he had wasted his big surge when he three-putted for bogey from just off the green 100 feet away, lipping out his 4-foot par attempt. But he reached the front of the 18th in two shots for a two-putt birdie.

It gave him a chance, and that was all Reed needed.

“I can’t do anything about him. I can’t control that,” Walker said. “I can control what I was doing, and I wasn’t doing my job.”