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On a day judged as much by elapsed time as games won, Rafael Nadal came out looking the freshest.

Nadal and Andy Murray won Friday to set up a semifinal matchup at the U.S. Open. They'll be back on the court Saturday — their third straight day of tennis at a tournament that has been forced into some drastic scheduling changes after losing two days to the rain.

Fourth-seeded Murray won a four-set grind against 28th-seeded John Isner, 7-5, 6-4, 3-6, 7-6 (2) that took 3 hours, 24 minutes.

No. 2 Nadal had a much easier time, topping slow-moving No. 21 Andy Roddick 6-2, 6-1, 6-3 in 1 hour, 53 minutes.

Or, to put it more simply, Advantage Nadal, even if staying fresh wasn't his top priority.

"I try my best," Nadal said. "I don't think about a short match for the quarterfinals. I think about trying to win the match."

The first semifinal Saturday pairs No. 1 Novak Djokovic against No. 3 Roger Federer in a rematch of their French Open semifinal, where Federer snapped Djokovic's match winning streak at 43. They won their quarterfinals Thursday and rested while Nadal and Murray played Friday.

This marks the first time the top four seeds have filled the final four slots at the U.S. Open since 1992, but the second time it has happened at a Grand Slam this year. At the French Open, Nadal beat Murray in one semifinal and went on to defeat Federer for his sixth title at Roland Garros.

"I think they're pretty firmly the best players in the world right now," Roddick said. "They certainly deserve the numbers next to their names. They're playing great."

Over the first six matches on his road to the U.S. Open title last year, Nadal didn't lose a set. He is on the same pace through five matches this year.

Though Roddick needed two visits from the trainer and was clearly showing signs of fatigue from a four-set win the day before, Nadal did his part by never giving the 2003 champion even a glimmer of hope.

The most impressive stat: Nadal's 22 winners from the forehand side, compared to none for Roddick.

"I think I am playing well since the second round," Nadal said. "I'm very happy about this U.S. Open. Doesn't matter. I will try my best to be in the final. But even if I lose tomorrow, I am happy about my U.S. Open. Wasn't an easy situation for me coming to this tournament after having a not easy summer for me."

Since winning the French Open, Nadal has lost his No. 1 ranking to Djokovic, along with a number of matches he would have often been expected to win.

Nadal is 12-4 lifetime against Murray, the only one of the semifinalists still without a Grand Slam trophy.

So far, Murray has spent 13 hours, 6 minutes on court in five rounds, compared to 10:50 for Nadal.

"I think on the American hard courts, it's a close, close matchup," Murray said.

Federer is 14-9 against Djokovic, though last year at Flushing Meadows, he lost to the Serb. Federer conceded that the thought of having to turn around and play Nadal the next day did creep into his mind while that match was going on.

"Still should have won the match maybe, but it's just a tough prospect," Federer said. "You never have it that we have to play back-to-back, best-of-5 matches and only here before the final at the U.S. Open. It just somehow doesn't make a whole lot of sense to me."

But Federer won't have to do it this time. There will be a day off before the Monday final, meaning Federer or Djokovic will end up playing three matches over five days, while the Nadal-Murray winner will play four in five. A big difference when it's best-of-5. Djokovic, however, isn't sympathetic.

"It has to be an advantage in some ways," Djokovic said. "That's the way it is. You can't fight it. You can't complain. It's Mother Nature that doesn't allow us."

This year, instead of capping off Saturday's men's semifinals with the women's final, there will be two women's semifinals. Angelique Kerber plays No. 9 Samantha Stosur, and No. 1 Caroline Wozniacki will face No. 28 Serena Williams, who is going for her 14th Grand Slam title. The winners of those matches will play Sunday, which is when the men's final was originally scheduled.