NEW YORK — Andy Roddick's legs felt fatigued.
The crowd at Arthur Ashe Stadium was hushed.
And defending champ Rafael Nadal was at his court-covering, groundstroke-whipping, serve-stopping best.
Overwhelming Roddick from the start, Nadal compiled a stunning 22-0 edge in forehand winners, broke six times and never left the outcome of their match in doubt, winning 6-2, 6-1, 6-3 Friday to reach the semifinals at the U.S. Open for the fourth consecutive year.
"The beginning of the match was really important," Nadal said. "Andy had a really tough match (Thursday vs. David Ferrer). Probably, he was tired. Sorry for him."
What was it like for 2003 U.S. Open champion Roddick to be out there, his own game faltering and Nadal's as good as it gets?
"It's a bad feeling. It's almost worse than competing," said Roddick, who was the last American man remaining in the Open. "You feel helpless."
Nadal took the first four games in 18 minutes. He then reeled off 16 of the last 17 points — including 12 in a row — to close the second set.
"It was quick. Obviously, it was a combination of things that probably weren't going to work out (Friday)," said Roddick, who had trouble pushing off on serves and forehands and was massaged by a trainer during a medical timeout in the third set.
Seeking his 11th Grand Slam title, Nadal has yet to drop a set heading into today's semifinal against No. 4 Andy Murray, who beat No. 28 John Isner 7-5, 6-4, 3-6, 7-6 (7-2).
"It will be a very tough match for me," second-seeded Nadal said, "and hopefully for him, too."
Nadal has won 12 of 16 matchups against Murray, including eliminating him in the semifinals of the French Open on clay and Wimbledon on grass this year. Now it's hardcourt.
"It's a good surface for me to play him on," said Murray, who played 1½ hours longer than Nadal did Friday. "It's a close, close matchup."
Murray weathered 17 aces from the 6-foot-9 Isner but did break twice in a row bridging the first two sets.
Isner was playing in his first Grand Slam quarterfinal and acknowledged that jitters affected him at the outset.
"I wasn't swinging out like I felt like I should have early on in the match. I was just guiding the ball," said Isner, a Tampa resident. "That was a little bit of nerves. It just took awhile to free up."
The exits by Roddick and Isner — with first lady Michelle Obama in the stands — mean this will be the 32nd Grand Slam tournament in a row without a male champion from the United States, extending the country's longest drought, which dates to Roddick's 2003 triumph in New York.
Today's other men's semifinal was set up Thursday: No. 1 Novak Djokovic against No. 3 Roger Federer. And for the second time in the past three major tournaments, the final foursome is filled by the top men ranked Nos. 1-4 — something that hadn't happened at the U.S. Open since 1992.
Women's semifinals: Serena Williams, seeded 28th, faces top-ranked Caroline Wozniacki in tonight's featured match, and No. 9 Samantha Stosur, a Tampa resident, takes on 92nd-ranked Angelique Kerber. Stosur is trying to reach her second Grand Slam final.