Kim Clijsters celebrates Tuesday after defeating Samantha Stosur in a quarterfinal at the U.S. Open Tuesday.

NEW YORK — Nobody can say Kim Clijsters took an easy path to her U.S. Open title last year. She played both Williams sisters.

This year, she'll only play one, though this could be an even more effective version of Venus Williams than came to Flushing Meadows in 2009.

Clijsters and Williams each won their quarterfinal matches Tuesday to set up a marquee semifinal: the No. 2 seed, Clijsters, vs. the No. 3 seed, Williams, and a pair of women both seeking a third U.S. Open championship.

"Just the ability to compete," Williams said when asked to describe her opponent. "I think in coming back from her layoff, I think she never lost that."

Last year, Clijsters returned from a 2½-year layoff and was hoping to use the U.S. Open as a bit of a tuneup and a test before she made the comeback in earnest in 2010.

In one of the best comeback stories of the year, she ended up winning the whole thing. It started looking like a real possibility when Clijsters beat Williams, who was visibly hobbling on an injured knee, 6-0, 0-6, 6-4 in the fourth round.

In last year's semifinals, a match remembered for a certain foot fault, Clijsters topped Serena Williams.

Serena isn't here this year because of an injury. Venus hurt her knee again, too, but recovered in time to play.

"This is probably some of the best of Venus that I've seen for a while," Clijsters said.

Maybe not the cleanest tennis, but certainly good enough to win. Williams overcame nine double-faults and a total of 33 unforced errors — much of it caused by a wind that whipped around Arthur Ashe Stadium for yet another day — to beat reigning French Open champion Francesca Schiavone 7-6 (5), 6-4.

"I feel like when the stakes were higher I was able to raise my game," Williams said.

In men's play Tuesday — "Spain Day" — No. 1 Rafael Nadal advanced with another three-set victory, this time over fellow Spaniard Feliciano Lopez. Nadal, who hasn't lost a set or a service game yet in the tournament, advanced to play No. 8 Fernando Verdasco, who defeated No. 10 David Ferrer, also of Spain, in a classic match, 5-7, 6-7 (8), 6-3, 6-3, 7-6 (4).

Another quarterfinal will pit No. 12 Mikhail Youzhny against No. 25 Stanislas Wawrinka.