Top-seeded Justine Henin clocked another qualifier at the U.S. Open, taking only 50 minutes today to breeze into a fourth-round matchup with no. 15 Dinara Safina.

Safina’s brother, a former Open champ, Marat Safin, was eliminated. He’s never rallied from a two-set deficit and the no. 25 Russian didn’t do it this time, smacking his last shot right into the net in a 6-3, 6-3, 6-3 loss to Stanislas Wawrinka of Switzerland.

“Everything I tried didn’t work out. It was kind of a weird match,” Safin said.

At least he made it through intact. Several players have needed help from trainers as the humidity and hard courts take their toll at the final Grand Slam of the season.

Henin shook off recent shoulder trouble to win the first 10 games, approach the net more often than usual and chase Ekaterina Makarova of Russia 6-0, 6-2.

Chances are, Henin knew it exactly how long it took. The righty wears a wristwatch on her left hand during matches.

“I cannot live without my watch,” she said. “I never saw another player playing with a watch. But I always keep my watch. I sleep with that. I take my shower. Everything.”

The former Open champion from Belgium beat her third straight opponent from outside the top 100. Not that she worried about getting a vigorous warmup.

“A big part of my success is that I’ve always been very focused on myself in the last few years,” Henin said. “Don’t look too much on the other side of the net.”

Next up for Henin is Safina. The Russian never permitted a break chance and chased American Ahsha Rolle 6-4, 6-3.

“Obviously, she has more experience than me,” Rolle said. “I feel like I had a couple of bad shot selections that kind of cost me big games.”

Rafael Nadal, Venus and Serena Williams, and the Serbian trio of Novak Djokovic, Jelena Jankovic, and Ana Ivanovic were scheduled to play later. So was Tim Henman, playing his last Slam.

Also, no. 17 Carlos Moya of Spain beat Igor Kunitsyn of Russia 6-4, 6-4, 7-5 and no. 20 Juan Ignacio Chela of Argentina defeated Wayne Odesnik 6-3, 6-1, 7-5.

On the women’s side, no. 10 Marion Bartoli of France beat Lucie Safarova of the Czech Republic 4-6, 6-2, 6-3.

As fans straggled into Flushing Meadows on an overcast day, there was talk about what happened the previous night, and what was coming up.

In a match that stretched from last night into early today, James Blake outlasted Fabrice Santoro 6-4, 3-6, 6-2, 4-6, 6-4.

Blake had been 0-9 in fifth sets, and this matched ended with both rackets on the court.

Blake dropped his when he lifted his arms, as much in relief as exultation. Santoro flung his toward the ball, a desperate and failed attempt to extend an entertaining U.S. Open match that went past midnight.

In a tournament where the favorites have ruled, the most intriguing match was set for tomorrow: a three-time Open champ, Roger Federer, vs. a 6-foot-9 rookie, John Isner.

“Isner’s going to be very tall,” a former winner, Andy Roddick, said, “and Roger’s going to be very good.”