SOUTHAMPTON, N.Y. — While Patrick Reed was winning the Masters in April, Brooks Koepka sat at home in Florida nursing an injured left wrist that had kept him off the golf course for most of the previous four months. He would not be cleared to take full swings with his wedges or irons until the Monday after his friends and PGA Tour competitors had departed Augusta National.

That did not leave much time for Koepka to prepare to defend his U.S. Open title. But his swing coach, Claude Harmon III, knew Koepka would be fine when he saw that he was glued to the television, watching the end of the Masters instead of the beginning of the Major League Baseball season.

The viewing choice augured well for Koepka, “who’s never really been a golf nerd,” said Harmon.

“He watched the Masters,” Harmon said, “and I really believe he fell in love with golf again.”

Koepka, 28, who considered himself a frustrated baseball player slumming in golf for much of his teens and 20s, endeared himself to golf nerds Sunday by becoming just the third professional to win consecutive men’s national championships in the post-World War II era, after Ben Hogan in 1950 and 1951 and Curtis Strange in 1988 and 1989.

“It’s really incredible,” Koepka said. “I couldn’t be happier.”

Koepka, who began the day in a four-way tie for the lead, closed with a 2-under-par 68 and a 72-hole score of 1-over 281 at Shinnecock Hills. He finished one stroke ahead of Englishman Tommy Fleetwood, who tied the record for a men’s U.S. Open round with his closing 63. It was the first time since 2013 that the winner had finished over par.

When Koepka won last year at Erin Hills in Wisconsin, he finished at 16 under, tying the U.S. Open record set by Rory McIlroy at Congressional in 2011. But Shinnecock, which hosted the Open for the fifth time, has been known to humble the world’s best golfers, as the late part of Saturday’s round demonstrated. Amid high temperatures and stiff winds, it produced soaring scores and a lot of criticism of the setup. Koepka, however, seemed unperturbed.

“You’ve got to keep going, keep plugging away and don’t get caught up in all the talk and just keep focused on what you’re doing,” he said after his victory, adding, “I enjoy being pushed to the limit. Sometimes, you feel like you are about to break mentally, but that’s what I enjoy.”

Dustin Johnson, who is Koepka’s training partner and close friend, posted a 70 for sole possession of third place at 3 over.

Koepka’s father was a pitcher in college, and Koepka said that if not for his struggles hitting fastballs, he probably never would have focused on golf. He has no problem hitting the long ball off golf tees, but his putting was his salvation in the final round, particularly the 7-footer he made for birdie at No. 10 and the 15-footer he drained at No. 11 to salvage a bogey.

“The one that was really massive for us was No. 11,” Koepka said, referring to himself and his caddie, Ricky Elliott. “That was like making a birdie,” Koepka added, “maybe even making an eagle, it felt like, because it could have been a big momentum shift there.”

Koepka’s milestone-making moment came at the expense of Reed’s stab at history. Reed, who closed with a 68 to finish in fourth place, at 4 over, was trying to become the seventh man, and the first since Jordan Spieth in 2015, to win the first two legs of a calendar Grand Slam. No professional has won every men’s major in the same year.

“I had a chance, I definitely had a chance,” Reed said. “Just too many missed putts, and at the end of the day, just needed to hit my approaches a little closer.”

Also Sunday:

Ryu wins LPGA event: GRAND RAPIDS, Mich. — So Yeon Ryu won the Meijer LPGA Classic for her first victory of the season and sixth overall, closing with a 5-under-par 67 for a two-stroke margin. The 29-year-old South Korean birdied the par-5 16th and par-4 17th and parred the par-4 18th to finish at 21-under 267 at Blythefield Country Club. Two strokes behind Anna Nordqvist and Lee-Anne Pace entering the round, Ryu had six birdies and a bogey in the final round.