Clijsters to Play Venus Williams in 4th Round

This is the sort of challenge that tempted Kim Clijsters back from a two-year retirement: a match against Venus Williams at the U.S. Open.

"She's been playing really well, and I've been playing really well, also," Williams said. "Obviously, it's great to see her back. But I want to advance to the next round."

Williams, the 2000-01 champion at Flushing Meadows, and Clijsters, the 2005 winner, set up a fourth-round meeting with victories Friday.

The No. 3-seeded Williams struggled with her serve, including seven double-faults, and appeared to have some problems with her left knee before pulling out a 6-2, 7-5 win over 46th-ranked Magdalena Rybarikova of Slovakia.

Williams' knee was again heavily bandaged, just as it was in the third round.

Asked afterward about how she felt, Williams said: "I had some challenging moments in the match, but I always run after the ball and try to hit it in the court. It's even better if I can hit a winner."

She only managed to come up with 18 winners against Rybarikova, but that was enough against an opponent who made 31 unforced errors.

Clijsters, meanwhile, beat Kirsten Flipkens 6-0, 6-2. Clijsters is playing at the U.S. Open for the first time since 2005.

Clijsters said she didn't plan to focus on Williams' knee too much.

"When you play against her, you know that the balls are coming fast," the Belgian said. "You don't really have time to worry too much about injuries or anything."

Williams and Clijsters have met 10 times, with the American holding a 6-4 edge. Their last meeting came in the 2005 U.S. Open, and Clijsters beat Williams in the quarterfinals on the way to the championship.

"It's been so long (since) I stood in front of someone like her, who can play as well as she can," said Clijsters. "I know what kind of tennis I have to bring."

The 26-year-old Clijsters left tennis in 2007, got married and had a child. But she returned to the tour last month, and will enter the rankings after the tournament.