"It was a very good practice for me, no?" the 23-year-old Nadal told reporters after his 6-0, 3-6, 6-3, 6-4 second round victory over German Nicolas Kiefer that closed out the night session on the fifth day of play at the National Tennis Center.
The 32-year-old Kiefer burst into life after a 24-minute first-set blitz from Nadal and slugged it out toe-to-toe with the Spaniard for the remainder of the match.
"Playing three hours is a very good test," said Nadal, who has competed in just two tournaments since shutting down his season for two months following the French Open because of tendinitis in his knees.
"At the same time it's important. First day, I didn't have any bad moment, any pressure moment," he said about his straight-sets opening win against France's Richard Gasquet.
"Today I had to do more."
Nadal won the last two sets on the strength of one service break in each but the muscular Spaniard held Kiefer at bay by not facing a break point after the second set.
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Kiefer, ranked as high as world number four in 2000, had never won a set against Nadal in four previous meetings.
"I think he was getting a little tired," the 129th-ranked Kiefer told reporters. "I could see it, I could feel it. He didn't move so good. But a win is a win, and a loss is a loss.
"Today was the first time I was thinking I could really beat him."
Nadal's victory meant that the top 16 men's seeds advanced to the third round for the first time in a Grand Slam.
"(There are) Very good players right now at the top," Nadal explained.
"The best players are winning. They don't have strange losses. I think that's good for tennis."
Nadal, however, was not as complimentary about the timing of his match.
"It's too late," he said. "One-fifteen (a.m.). I have to have dinner. Before 3:30 a.m. is impossible to be sleeping. I think it is a little bit late."
Told he could ring his friends back home in Mallorca because it would be after seven in the morning there, Nadal smiled.
"Yeah. They're probably coming back from a party," he said.
Nadal's third-round opponent will be countryman Nicolas Almagro, who edged out American Robby Ginepri in five sets.