NEW YORK -- He emerged from the locker room Monday looking a little crusty around the edges. Rafael Nadal was five minutes late for his off-day hit on Practice Court 1, but he walked slowly, three rackets cradled in his arm.
It was the morning after a bizarre cramping episode in mid-interview that sent a shiver into this U.S. Open. He told the crowd pressed against the barricade that he would sign autographs after the 45-minute session. Uncle Toni Nadal, catching the look of concern on the faces of Spanish journalists, smiled wanly and gave them a thumbs up.
Rafa, we are happy to report, showed no visible signs of distress. The long-term prognosis may not be so encouraging.
People around the game were quick to downplay the event -- Nadal appeared to be in intense pain and was incapacitated for nearly 10 minutes -- as commonplace, but for those who haven't witnessed it first-hand, it was a window into the physical hardships of playing professional tennis. It was, Nadal later told Spanish writers, just bad luck that it happened in so public a place.
Even before his right leg locked up, Nadal had been struggling with some niggling issues in a third-round match against David Nalbandian. The top of his index and middle fingers of his right hand were heavily taped, the fallout of a strange restaurant accident involving a hot plate. The four fingers on his business hand, the left, were also taped as usual. Early in the third set, Nadal was visited by an ATP World Tour trainer, who treated blistering on his right foot.
Nadal always has been a truth-teller and he has been open about the demands of the sport on his body. He can even make light of it.
Discussing the timing of his recently published autobiography, "Rafa," on Monday, he told the media, "We thought it was the right time to do it, even if I am at the beginning of my career."
He winked when he said it.
Nadal turned 25 three months ago and is relatively young in the context of the general population. But in tennis terms, he is approaching old age; if he were a car, his odometer would be somewhere past 200,000 miles.
He began playing tennis with Toni in Mallorca, Spain, at the age of 4. That means he's been at it for well over 80 percent of his life. The combination of Nadal's physical style of play and the heft of his schedule are extraordinarily taxing on his body. Nadal has been a victim of his own success, too, going deep in virtually every event he plays. Since 2005, when he broke into the top 10, Rafa has played 565 matches -- more than any other ATP player. And although, Roger Federer has played nearly as many, 547, the economy of his fluid game has left few scars. Nadal, according to a graphic in the New York Times, sometimes creates 5,000 revolutions per minute on a tennis ball with his savage forehand, and typically averages a number 20 percent greater than Federer. Well, there is a physical price to pay for that extra torque and we are seeing it more and more.
Nadal turned professional in 2001 but did not play the tour full time until two years later -- when he was 16. His knees have been a concern for years and an injury to his left foot in 2005 has caused him pain ever since.
After his cramp attack, Nadal spoke briefly with Spanish reporters and walked to the players' garden for an interview with Tennis Channel. He said he was OK.
"I think for everybody is tough," Nadal told Justin Gimelstob. "Maybe for me is tougher because I started earlier than everyone else. Nine years in tennis -- that is a long time. Many people do not play that long.
"When you put your body at the limit, you're going to have problems."
On Tuesday, Nadal plays unseeded Gilles Muller of Luxembourg for a berth in the quarterfinals.
Enjoy Rafa while you can. His shelf-life is limited.
0-for-ever: Normally, No. 4-seeded Andy Murray would have reason to be confident for a fourth-round match at a Grand Slam. He might have some doubts, however. He meets 22-year-old American Donald Young -- who beat him earlier this year at Indian Wells, 7-6 (4), 6-3, in their only previous encounter.
Channeling 2003: It's been eight years since Andy Roddick broke through with his first major victory here at the U.S. Open. Tuesday, we'll see if he can recapture that form against a tough opponent, No. 5 seed David Ferrer, a semifinalist here in 2007.
Final answer: Last year, Vera Zvonareva advanced to two major finals. This year, the No. 2 seed could do it again. Zvonareva meets the toughest player left in her half of the draw, No. 9 seed Samantha Stosur.
Greg Garber is a senior writer for ESPN.com.