Greller reminded Spieth that he belonged in that photograph.
“You’re that caliber of athlete,” Spieth recalled Greller saying. “But I need you to believe that right now, because you’re in a great position in this tournament.”
From the lousiest position possible, Spieth spent 20 minutes setting up the shot that would make Greller’s words ring true. Spieth accepted a one-stroke penalty for an unplayable lie and, taking care to follow the rules about a drop, backed way up — until he reached the practice range.
Even though Spieth felt certain that the distance to the pin was 270 yards and that he should use a three-wood, he trusted Greller’s assessment: 230 yards to the pin and a three-iron.
Hitting toward a pin that he could not see, Spieth landed his next shot between two bunkers protecting the green. Then he pitched to 8 feet and made the putt for a bogey 5 that left him at seven under, one stroke behind Kuchar, who made par after the lengthy wait.
For the first time all weekend, Spieth was the challenger, not the pursued, and he found that freeing. His focus became laser sharp. He played the final five holes in five under to post a one-under-par 69 and a 72-hole score of 12-under 268 for his third victory in a major. He finished three strokes ahead of Kuchar, who also posted a 69.
“All of the sudden, the lid came off,” Spieth said, referring to an imaginary cover over the hole. He nearly aced the par-3 14th. He drained a 48-footer for eagle on the par-5 15th, made a 25-foot birdie putt at the par-4 16th, birdied the 17th after a textbook chip, and two-putted the 18th for the easiest par of a long and trying day.
“Closing today was extremely important for the way I look at myself,” said Spieth, who is a P.G.A. Championship title away from becoming the sixth man to complete a career Grand Slam, joining Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Tiger Woods. Spieth, who won the Masters and the United States Open in 2015, became the second male golfer to win three majors before his 24th birthday, joining Nicklaus, the 18-time major winner.
Spieth, who will turn 24 on Thursday, described comparisons to Nicklaus as “amazing” but said, “I don’t think that they’re appropriate or necessary.”
He added: “In no way, shape or form do I think I’m anywhere near that, whatsoever. So it’s a good start, but there is a long way to go.”
Zach Johnson, who won the 2015 British Open in a three-man playoff after Spieth bogeyed the penultimate hole to finish one stroke back, disagreed. He said Spieth’s sophistication at this stage of his career was “hard to fathom,” pointing to Spieth’s escape act at 13 as a perfect illustration.
“Those are the intangibles, and the things I just don’t understand,” Johnson said, “I’m not suggesting I can’t do it. He just does it all the time.”
The victory was Spieth’s 11th in a PGA Tour-sanctioned event since he turned pro in 2012. Only Woods, with 15, collected more before his 24th birthday. The third-ranked Spieth is one of five golfers in his 20s in the world’s top seven. The millennial movement that is occupying men’s golf shows no signs of dissipating. The two lowest scores at the British Open were a closing 63 by a 21-year-old, Li Haotong of China, who vaulted into third place at six under for the tournament, and a majors record of 62 in the third round by a 29-year-old, Branden Grace of South Africa.
Kuchar, 39, has played in 47 majors, without a win, and this was only his second top-10 finish in the British Open. It is not easy to keep pace with the youngsters who are transforming the men’s game, and at the trophy ceremony on the green, a teary Kuchar looked like a man unsure of how many more times he would be so well placed to win a major.
“It’s crushing,” Kuchar said, adding, “To be this close, to taste it with five holes to go, it’s a hard one to sit back and take.”
Kuchar’s wife, Sybi, and two sons, Cameron, 9, and Carson, 8, cut short a vacation in Colorado to travel here as a surprise and cheered him on in the final round. Outside the scoring area, Spieth stumbled upon Kuchar’s boys and saw that Cameron was crying.
“At that moment,” Spieth said, “I’m so happy, and at the same time I see that and I thought to myself, ‘Man, put this in perspective, he’s a dad.”
Spieth is still the son, who was consoled by his father, Shawn, after disappointments like the 2015 British Open and 2016 Masters. And he is headed down a path only a select few have traveled.
Ernie Els, speaking after his round of 74, while Spieth was still on the course, said he believed that Spieth could challenge Woods’s 14 major victories.
“He can go up to the 14 mark,” said Els, who explained that Spieth’s track record — seven top-four finishes in 19 major starts — was going to intimidate any opponent who saw his name on the leaderboard.
“Guys kind of start knowing that you know how to win,” Els said. “And almost like Tiger, where people maybe feel like they can’t do it against Jordan.”