Next up is the PGA Championship at Whistling Straits. And if the Grand Slam is no longer in play, there's still plenty out there.
"I don't know how many guys have done three majors in a year," Spieth said. "I'm sure there's only been a few."
Very few, actually.
Ben Hogan did it in 1953, winning the Masters, U.S. Open and British Open. Tiger Woods missed in the Masters but won the last three majors of the year in 2000 on his way to what became known as the Tiger Slam.
After his chances at winning his third straight major evaporated with a couple of missed opportunities on the last two holes Monday, Spieth was already looking ahead.
It was hard not to after coming up one shot short of a three-man playoff that Zach Johnson won over Louis Oosthuizen and Marc Leishman in what otherwise might have been a British Open for the ages at the home of golf.
Besides, the 21-year-old golfing sensation was not going to get too down after failing to add the claret jug to his Masters green jacket and U.S. Open trophy.
"I made a lot of the right decisions down the stretch and certainly closed plenty of tournaments out, and this just wasn't one of those," Spieth said. "It's hard to do that every single time. I won't beat myself up too bad because I do understand that."
A missed 8-footer on the treacherous 17th hole helped seal Spieth's fate on the Old Course. A misplaced drive on the final hole did the rest.
He could also point to four putts from 120 feet on the eighth green where he tried to get greedy on his first putt. But Spieth followed that with back-to-back birdies, something he tends to do when things go bad.
Something he also tends to do is pay respect to the game and its fans. He's been described as a young man with an old man's wisdom, and it showed in the way he took what had to be a most bitter defeat.
When Spieth walked off the green, he applauded the fans who cheered him on. Later, he came out and watched Johnson win a playoff, then gave him a congratulatory hug.
Johnson earned it.
Starting the final round three shots behind, he shot 31 on the back nine and took the lead with his seventh birdie of the round on No. 12. It looked as though his hopes were slipping away when his right foot spun out on his second shot at the 17th that led to bogey. But with the most significant shot of the tournament, Johnson holed a 30-foot birdie putt on No. 18 for a 6-under 66 and was the first to post at 15-under 273.
Leishman, who lost the lead with a bogey on the 16th hole, had a birdie putt on the 18th to win that stayed left. He shot 66. Oosthuizen saved par on the 17th with a 10-foot putt and made a 5-foot birdie on the final hole for a 69 to join the playoff.
Johnson opened with two quick birdies, kept a one-shot lead in the playoff when Oosthuizen missed a 5-foot par putt on the 17th hole and won the Open when the South African — the last player to lift the jug at St. Andrews in 2010 — narrowly missed a 12-foot birdie attempt.
"I'm grateful. I'm humbled. I'm honoured," Johnson said. "This is the birthplace of the game, and that jug means so much in sports."
He knew Oosthuizen or Leishman easily could have won. And he felt the same about Spieth.
"I can't describe the magnitude as to what he was going through because I've never been in that position," Johnson said. "We haven't really seen that with the exception of Tiger. Truthfully, he could be hitting here.
"He's a phenomenal talent," Johnson said. "And I'm telling you right now, he's a better person than a golfer."
Golf hasn't seen such a player since the days of Tigermania. And there's no reason to believe that Spieth can't continue to contend — and win — major titles for a long time to come.
"I'm very pleased with the way I played," Spieth said. "I think the way that I played this week and especially today would have won the U.S. Open by more than just a shot. I didn't play as well there. It's just that's the kind of golf that was played by the field this week, it just took some special golf. Whoever comes out the champion, that's a hell of a major."
In other words, Spieth didn't lose the tournament. Someone else simply came along to beat him.
Spieth will take that attitude to Whistling Straits, the third straight links-style course among the year's majors. He'll be favoured there again, with a chance to join some elite company as a winner of three majors in one year.
No sense thinking too much about what might have happened. No need to think about how close he came to be playing in Wisconsin for golf immortality.
"It's a tough feeling to be that close in a major," Spieth said. "I believe I'll have plenty of opportunities like I did today but, still, when it doesn't work out it's tough to swallow a little bit."