After struggling for so many years to win his first major, Andy Murray arrived at the U.S. Open this year laden with all the titles of a tennis royal.

But the reigning Olympic gold medalist, first-time Wimbledon champion and defending U.S. Open champion got off to a churlish start, peeved by a puzzling schedule that had him cooling his heels for the tournament’s first three days and back-loaded his matches as a result.

Through five rounds of play, Murray muttered under his breath, let winnable sets slip away and labored so hard at times that he appeared injured when he was merely ill-tempered.

On Thursday at Arthur Ashe Stadium, with a place in the U.S. Open’s semifinals at stake, the man who ought to have felt on top of the tennis world tumbled hard, falling in straight sets to ninth-seeded Stanislas Wawrinka, who did just about everything right en route to a 6-4, 6-3, 6-2 victory.

Murray was in contention well into the opening set, with neither managing to break the other’s serve through nine games.

But serving at 4-5, Murray couldn’t summon the strokes to get past the stubborn Wawrinka, whose career has been overshadowed by that of Switzerland’s favored son, 17-time Grand Slam champion Roger Federer. Five times Murray fended off break points in that game against Wawrinka, who had never advanced beyond the quarterfinals of a major. On the sixth break point, Murray blasted a forehand long and cracked his racket on the court in disgust.

Given Murray’s experience in big matches, combined with Wawrinka’s lack of it, it was reasonable to expect the Scot to turn the match around. But instead of taking command, he reverted to counterpunching, hitting a total of seven winners in the two sets that followed to Wawrinka’s 29.

“I don’t know if I’m meant to win every Grand Slam I play or be in the final,” Murray said in response to one in a series of questions seeking an explanation for his subpar play. “With the guys around now, it’s very challenging. I’ve played my best tennis in [Grand] Slams the last two or three years. I lost today in straight sets. I would have liked to have gone further.”

Wawrinka was overjoyed at toppling the tournament’s defending champion. It marked the first time he had gone further in a Grand Slam than Federer, his compatriot and Davis Cup teammate, who fell in the fourth round.

His victory was well deserved. The shortcomings in Murray’s play, for the most part, were a result of the pressure Wawrinka put on him from start to finish, consistently placing the ball precisely where he wanted it.

The Swiss served exceptionally well, winning the point on his first serve 88 percent of the time. Murray never managed a single break point against him but faced 11 break points himself.

Trailing two-sets-to-none, Murray double-faulted to get broken early in the third set. He was broken again after following a short approach shot to the net and getting passed by a clean winner.

Afterward, Murray declined to revisit the scheduling issue that irritated him so at the tournament’s outset but gave all credit to Wawrinka.

“He played great,” Murray said. “He hit big shots, passed extremely well, hit a lot of lines on big points and served well.”

Wawrinka next faces top seed Novak Djokovic, who overcame a sloppy third set to defeat a spirited challenge from 21st seed Mikhail Youzhny 6-3, 6-2, 3-6, 6-0. Saturday’s other semifinal will pit No. 2 seed Rafael Nadal against eighth-seeded Richard Gasquet.

Asked whether he might be emotionally drained from his Wimbledon triumph in July, which prompted wild celebrations throughout Britain and talk of knighthood for the Scot, Murray halfway allowed for the possibility.

“When you work hard for something for a lot of years, it’s going to take a bit of time to really fire yourself up and get yourself training 110 percent,” said Murray, whose victory ended a 77-year wait for a British male champion. “That’s something that I think is kind of natural after what happened at Wimbledon. But I’ve been here [in New York] nearly three weeks. I’ve practiced a lot, played quite a lot of matches. I prepared properly.

“It’s a shame I had to play a bad match today.”

Earlier Thursday, Americans Bob and Mike Bryan were stopped short in their quest to claim a calendar-year Grand Slam in men’s doubles with a semifinal loss to the fourth-ranked team of Leander Paes and Radek Stepanek.

The Bryans led the series 4-3 and had won 36 of their last 37 matches. But after claiming the opening set, they committed a series of uncharacteristic errors, while Stepanek and the 40-year-old Paes, a fixture on the Washington Kastles, raised their play to pull off the 3-6, 6-3, 6-4 upset.

The Bryans, who boast a record 15 Grand Slam titles, were seeking to become the first men’s doubles team since 1951 to win all four majors in the same year.

Meanwhile, Venus and Serena Williams advanced to the women’s doubles semifinal with a 6-3, 6-1 victory over Italians Robert Vinci and Sara Errani.