NEW YORK (AP) - Sweating through a pivotal game in a match that was becoming more difficult than expected, Rafael Nadal finally broke through.
He hit his winner, pumped his fist three times and shouted "Vamos!" - Let's Go.
About an hour later, he was, indeed, safely off the court and into the third round, capping off a clean sweep for the top 16 players at the U.S. Open.
They are 32-0 through two rounds, the first time that's happened in the 41-year history of Open-era Grand Slam tennis.
The third-seeded Nadal defeated Nicolas Kiefer 6-0, 3-6, 6-3, 6-4 in a three-hour match on an electric Friday night at Arthur Ashe Stadium.
"A very good practice for me, no?" Nadal said. "To play in three hours is a very good test. At the same time, it's important. The first day, I didn't have any bad moment, any pressure moment. Today, I had to do more."
Didn't look like he would at first.
The first set took only 24 minutes. But Kiefer, the 129th-ranked player and the boys U.S. Open champion back in 1995, won the second and matched Nadal game for game deep into the third. Nadal finally got his break to make it 5-3, which brought on his celebration.
A tougher test than expected? Yes.
A welcome test for Nadal, who missed Wimbledon with bad knees? Of course.
Impressive? Depends on who you ask.
"He was getting a little bit tired," Kiefer said. "I could see it, I could feel it. He didn't move so good. But at the end of the day, it doesn't count if you play good or bad. A win is a win, a loss is a loss."
On the women's side, the Williams sisters both advanced in straight sets, as did Kim Clijsters, who set up a fourth-round match with No. 3 Venus Williams. Clijsters took two years off and has played so little tennis since she came back, she's not even ranked. She looked good Friday against Kirsten Flipkens in a 6-0, 6-2 victory. Venus, still wearing heavy tape on her left knee, had to work hard for a 6-2, 7-5 victory over Magdalena Rybarikova.
"It's been so long (since) I stood in front of someone like her, who can play as well as she can," Clijsters said. "I know what kind of tennis I have to bring."
Breaking through. It's the same challenge the men are facing, as the top tier on that tour continue to separate themselves from the rest this year.
"The best players are winning and they don't have any strange losses," Nadal said. "I think that's good for tennis."
Nadal and No. 2 Andy Murray, who defeated Paul Capdeville of Chile 6-2, 3-6, 6-0, 6-2 on Friday, are the only two players in the top 10 to have dropped as much as a set over their first two rounds at Flushing Meadows.
And not just here.
At the Montreal Masters hard-court tournament in August, the men ranked Nos. 1-8 filled the eight quarterfinal berths - the first time that's happened at an ATP tournament since rankings were introduced in 1973. The next week, at the Cincinnati Masters, the top four men made the semifinals.
"There is a gap," said Jurgen Melzer, who lost to No. 6 Juan Martin del Potro 7-6 (6), 6-3, 6-3.
Capdeville sees it, too.
"I can say that there are moments when you start thinking that other guy is so clearly superior to you," he said. "But I never go out to play thinking I will lose beforehand."
The dominance at the top didn't mean there weren't competitive matches on the grounds. American Taylor Dent put on a stirring show in a five-set, 4-hour victory over Ivan Navarro of Spain, 6-4, 5-7, 6-7 (1), 7-5, 7-6 (9).
Dent grabbed the umpire's microphone after the match and thanked the crowd. His inspirational comeback story - he nearly saw his career ended by a back injury - hits a likely roadblock when he meets Murray in the third round.
"It's going to be rough, there's no way around it," Dent said. "My execution is not where I want it to be, but that's not going to stop me from battling. That's how I won today. Even if it's 6-0, 6-0, 6-0, I'm going to go out and hustle and give everything I've got."
The same should be expected from 2001 champion and 31st-seeded Lleyton Hewitt, who will try to snap a personal 13-match losing streak against No. 1 Roger Federer, along with Federer's 36-match winning streak at the Open. They play Saturday in Ashe Stadium.
Also up Saturday is 17-year-old American Melanie Oudin, who faces 29th-seeded Maria Sharapova, playing well in her return to the U.S. Open after missing last year with an injured shoulder.
No. 5 Andy Roddick plays fellow American John Isner, and first-seeded Dinara Safina, who has needed nearly 5 hours and six tough sets to get through her first two matches, plays 72nd-ranked Petra Kvitova.