UNIVERSITY PLACE, Wash. — The endless recurring theme of the U.S. Open is the gruesome losing shot on the final hole that no one foresees — especially the victim — because it is an almost incomprehensible mistake not normally factored into golf’s equation.

The possibility of something evil, which almost never happens, drifts to the edges of the great golfer’s mind until, suddenly, that one misplaced thought, that one caution against the worst possible disaster, comes back to strangle his last chance. Yet that’s the U.S. Open’s signature, so often written in someone’s blood.

Now Dustin Johnson will get to ask so many others, from the great Phil Mickelson who double-bogeyed the 18th at Winged Foot to the careless Stewart Cink, who botched a one-foot putt to miss an Open playoff, how can that happen?

From four paces from the cup, with a chance to become the first man ever to win the U.S. Open by a shot with an eagle on the 72nd hole, why would the mighty Johnson worry about three-putting to lose by a shot? Thousands of fans in the crowd could two-putt from 12 feet 4 inches to tie.

Why would Johnson fret about handing his nation’s title to Jordan Spieth, who also won the Masters in April? You don’t come close to being great — and Johnson is ranked 10th in the world — by focusing on what almost never goes wrong.

After playing the first 601 yards of the 18th hole in two monstrously long and impeccably precise shots, why would Johnson worry about needing three taps on a putt with no particularly severe slope or speed?

Here is one reason. Johnson ranks 159th on the PGA Tour in putting inside six feet. That is his weakness — a pronounced and intractable one in his career.

Then, with a gasp, the entire golf world says, “Dustin Johnson just three-putted from 12 feet, the last putt from only four feet, to lose the Open by one shot. That didn’t really just happen, did it?”

“I just wanted a chance in the playoff,” said Spieth, meaning the Monday 18-hole playoff that the antiquated USGA still uses to decide 72-hole ties.

Instead, as the golf world started to party at the delicious thought, Spieth began talking about his quest for the third leg of a 2015 grand slam next month at St. Andrews in Scotland. And why not? Chambers Bay is almost shamelessly modeled on St. Andrews’ hump-and-bump links. If Spieth, a magical putter, could win on the awful poa annua infested greens here, might he not do even better at St. Andrews?

“You can’t win ’em all unless you win the first two, I guess,” said Spieth, who doesn’t shy in the least from Slam talk and understands that, at age 21, he has already done deeds that put him in the early-career company of the greatest. “We’re going after the Claret Jug [the British Open prize]. I believe we will be able to get it done if we get the right prep [work] in.”

Why shouldn’t Spieth have such amazing confidence? In April at the Masters, Spieth showed his immense and historic talent, tying Tiger Woods’s all-time scoring mark and lapping the field. This win was the antithesis of that cake walk. This was a slog, a battle for a 21-year-old not to lose faith — even a little — in his huge self-image.

All week here Spieth conceded that while most of his game was sharp, his driving was inconsistent and, he feared, not quite good enough to win an Open. Yet Spieth, in a four-way tie to start the day, never lost poise. When Johnson threw away a two-shot lead with ugly bogeys at the 10th, 11th and 13th holes, Spieth stepped into the leader board vacuum and, after birdies at the 12th and 16th holes, had what seemed like a huge three-shot lead. The Open was his to lose.

And he almost lost it. After a weak shot to the right-front junk at the par-3 17th, he hit a pitch shot fat, began taking animatedly at his ball and, for the only time all week, seemed rattled. Three putts followed and, in a blink, this Open was more complex than a crossword puzzle in Sanskrit.

Louis Oosthuizen birdied six of the last seven holes — yes, that is not a typographical error — to reach 4 under par. If only he hadn’t been riding in the same clown car on Thursday with Tiger Woods (80) and Rickie Fowler (81), maybe he wouldn’t have shot a 77 from which he had to unearth himself all week.

“I have to believe that I could find one or two shots in that 77 that I could have done less,” said Oosthuizen, a former British Open champ.

Spieth composed himself with two magnificent shots at the 18th to give himself an 18-foot putt for eagle to reach 6 under par. Like Johnson, he missed his eagle putt. But the young Spieth was wary not to leave himself a tough second putt. On such a tiny bit of wisdom or presence of mind great things can turn.

When Johnson missed his final four-foot putt to lose, Spieth said he thought, “There’s no way.” But he quickly added, “As the round went on and the green baked out and got even harder, anything outside two feet was not easy. Those are tough putts. That’s why I was so focused on those two-footers coming to the end.”

This is the fourth time Johnson has had a prime chance to win a major. And it is the fourth time that his composure, his putting or his lack of a golfing sixth sense of possible danger undid him.

As he left the 18th green, Johnson and his wife, Paulina, as well as their infant son, walked away. Johnson cradled the child in his arms. Infants can’t ask what millions around the world all said: “How the devil did that happen.”

It’s the U.S. Open. The devil’s everywhere, especially in those 12-foot 4-inch details.