NEW YORK – Many have been curious about the condition of Rafael Nadal’s knees, so it made sense that his first Grand Slam opponent in three months would wonder as well.

Which might explain why Richard Gasquet tried a drop shot deep in the third set of his U.S. Open match against Nadal on Wednesday. Nadal made the long run necessary to get to the ball, and flipped it back over the net, winning the point.

A moment later, as if conspiring with Nadal to show everyone how fit the six-time major champion truly is these days, Gasquet offered up another drop shot.

Nadal got to that one, too.

Starting a bid to win the only Grand Slam title missing from his résumé, Nadal encountered no apparent trouble from his much-scrutinized legs in a 6-2, 6-2, 6-3 victory over Gasquet at Flushing Meadows.

Gasquet, for one, was impressed.

“He can win the tournament,” said Gasquet, a 2007 Wimbledon semifinalist and former top-10 player. “Day after day, he will improve his level. For sure, he can win.”

Nadal’s matter-of-fact assessment: “I played well, no?”

One could certainly make the case Nadal wasn’t facing the toughest competition. Gasquet has been away from the tour, too, recently. He served a 21/2-month ban after testing positive for cocaine; Gasquet successfully appealed what would have been a far more severe punishment, saying the drug entered his system inadvertently when he kissed a woman at a nightclub.

Nadal’s absence was far more run-of-the-mill. He hadn’t played at a major tournament since May 31, when his 31-match French Open winning streak ended in the fourth round at Roland Garros. The Spaniard cited knee tendinitis in deciding not to defend his Wimbledon title, and the layoff was a big reason Nadal has dropped from No. 1 in the rankings to No. 3.

He ceded the top spot to Roger Federer, whose bid for a sixth consecutive U.S. Open championship – and third Grand Slam title in a row this year – progressed with a 6-3, 7-5, 7-5 victory over Simon Greul in front of a night-session-record crowd of 24,206.

Next for Federer is a matchup against two-time major winner Lleyton Hewitt, who dispatched Juan Ignacio Chela, 6-3, 6-3, 6-4. Federer has won 13 matches in a row against Hewitt, including the 2004 U.S. Open final.

The defending women’s champion, Serena Williams, was spectacularly good in eliminating 51st-ranked Melinda Czink of Hungary, 6-1, 6-1, in 53 minutes in the day’s last match.

Venus Williams, the 2000-01 champion in New York, had wide patches of white tape above and below her left knee, which began bothering her when she struggled through a first-round win Monday. Like Nadal, Williams looked hale Wednesday, and she easily dispatched Bethanie Mattek-Sands of the United States 6-4, 6-2.

“She was moving like a cat,” Mattek-Sands said.

Kim Clijsters, who ended her two-year retirement in August, continues to play as if she never left. Unseeded and unranked and playing at the U.S. Open for the first time since winning the 2005 title, the 26-year-old Belgian reached the third round by knocking off No. 14-seeded Marion Bartoli, 5-7, 6-1, 6-2.

Other seeded women sent home included No. 15 Samantha Stosur, two-time major champion Amelie Mauresmo, No. 12 Agnieszka Radwanska and No. 20 Anabel Medina Garrigues.

Two fixtures on the men’s tour said goodbye to Grand Slam tennis with first-round exits: Marat Safin and Fabrice Santoro. Both are retiring at the end of the season.

The 29-year-old Safin, the 2000 U.S. Open champion, lost to Jurgen Melzer, 1-6, 6-4, 6-3, 6-4; the 36-year-old Santoro, appearing in his record 69th major tournament, was beaten by No. 24 Juan Carlos Ferrero, 6-4, 6-3, 6-3.