Eventually, Nadal offered something of a complicated answer.
"I have to say that I am very well, because the results have been amazing since I came back," he said. "If I say something else, [it] will sound strange."
That's because when the year's last Grand Slam tournament begins Monday, none of the players setting foot on the blue hard courts of Flushing Meadows possesses as much momentum or is in as fine form as the No. 2-seeded Nadal. He's won his past 10 matches heading into the first round against the 97th-ranked Ryan Harrison of the United States.
Another past U.S. Open champion on Monday afternoon's schedule is 2000-01 winner Venus Williams, a former No. 1 now ranked 60th who will be taking on recent Wimbledon semifinalist and 12th-seeded Kirsten Flipkens of Belgium. At night, Williams' younger sister Serena, the defending champion, plays 2010 French Open winner Francesca Schiavone of Italy, while 17-time major champion Roger Federer faces 62nd-ranked Grega Zemlja of Slovenia.
The biggest curiosity when it comes to Nadal these days is how his knees will hold up. They've presented recurring problems for him over the years, particularly the left one, which kept him out of action from late June 2012 until February 2013. He missed the London Olympics, last year's U.S. Open and this year's Australian Open.
"I feel more comfortable now than six months ago, that's for sure," the 27-year-old Nadal said, then quickly added: "But I still have pain some days."
Hard courts could exacerbate the matter because of the pounding legs take on the unforgiving surface. Yet Nadal's been successful everywhere, winning the Australian Open and U.S. Open once each, along with Wimbledon twice, to go along with his record eight championships on the slower red clay of the French Open. Nadal is 15-0 on hard courts in 2013, with his current run of victories built en route to titles at Montreal and Cincinnati.
"He's going to be very difficult to beat here," said Andy Murray, the defending champion and No. 3 seed.
Top-seeded Novak Djokovic, who won the 2011 U.S. Open, said: "Nadal is definitely back, and he's playing maybe the best tennis that he ever has played on hard courts. ... He seems like he changed a little bit the game. He stepped in a little bit more. He knows that now he has to be a bit more aggressive than he usually is because of, I guess, his knees and everything and because hard court is not clay. It's not his favorite surface; it's faster. I'm sure he worked on that."
O Monday, 11 a.m., 5 p.m.
TV • ESPN2