Murray's managed only 15 winners, 30 fewer than Wawrinka. He tapped in some very slow second serves which allowed the Swiss to hit four return winners and easily take control of countless other points. Murray, one of the sport's top returners, never earned a single break point.
"I have had a good run the last couple of years," Murray said. "It's a shame I had to play a bad match today."
"I didn't get into enough return games, which is disappointing for me. That's normally something I do pretty well. I always give myself opportunities to break serve, and I didn't today."
At age 28, Wawrinka finally made it further at a major tournament than his Swiss Olympic teammate and good friend Federer, who lost in the fourth round and sent a congratulatory text to Wawrinka after his breakthrough victory.
"Today, for sure, it's my moment," Wawrinka said.
Asked what part of his performance made him the most proud, Wawrinka said: "How I was dealing with the pressure. Normally, I can be a little bit nervous and I can lose (a) few games because of that."
Murray was frustrated at his own errors in the 22-point final game of the first set, with muttering, eye-rolling and slaps to the forehead eventually giving way to some unbridled racket abuse.
The second set slipped away even faster, with Murray hanging his head after a forehand into the net closed a 12-point and three-game run for Wawrinka that made it 5-2.
At the end of that second set, he shook his hands in front of his face and screamed, infuriated by his own errors and inability to match what he perceives is unrealistically high expectations.
"If I'm meant to win every Grand Slam I play or be in the final, it's just very, very difficult just now," said Murray. "With the guys around us, it's very challenging."
Djokovic used his typical relentless defense to reach the U.S. Open semifinals for the seventh year in a row.
"Level of confidence is right at the top, very close, because I have been playing most of my matches here very aggressive, very dominantly," Djokovic said. "Even though I dropped a set, I feel I was in control."
He won the first 14 sets he played these two weeks, taking under two hours to advance each time. But he faltered against Youzhny in the third, making 16 unforced errors and getting broken twice the only service games Djokovic lost in the match.
"After I lost (the) third set, I definitely tried to regroup and focus on every point individually and start playing the same game that I had in first two sets," Djokovic said.
The Serb broke at the first opportunity in the fourth set and was untroubled from there.
Djokovic saved the first seven break points he faced, displaying his trademark ability to get his racket to balls he has no right to, and somehow turn such points around.
"Every point, you have to play. He never (misses)," Youzhny said. "He never (gives) you some presents."
Djokovic has won 12 of 14 tour matches against Wawrinka, including the past 11. The most recent came at January's Australian Open, when Djokovic edged Wawrinka 12-10 in a fifth set en route to the championship.
"Definitely one of the most exciting matches I have played in my life on this surface," Djokovic said.
The women's semifinals are Friday, with No. 1 Serena Williams vs. No. 5 Li Na, and No. 2 Victoria Azarenka vs. unseeded Flavia Pennetta. Williams owns 16 Grand Slam titles; the other women own three combined.
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