NEW YORK -- Serena Williams has yet to find anyone who can push her for two sets or beat her in one at this year's U.S Open.
Next to give it a try: none other than the top-ranked player in the world, Caroline Wozniacki.
Williams and Wozniacki each won in straight sets Thursday to set up a semifinal meeting at Flushing Meadows in the headliners' half of the draw. Williams defeated No. 17 Anastasia Pavlyuchenkova, 7-5, 6-1 and Wozniacki beat No. 10 Andrea Petkovic 6-1, 7-6 (5).
But the Williams-Wozniacki match will be the feature attraction on Saturday evening -- a day later than originally scheduled because of rain that washed out two days of play.
There is Williams, the power player and the only woman left who knows what it's like to win a Grand Slam title; she has 13. And there is Wozniacki, the quintessential counterpuncher, who has risen to No. 1 with her consistency but has yet to break through at the highest level.
This will be Wozniacki's first match against Williams since she became No. 1 -- as good a chance as any to show the world she belongs there.
But she doesn't feel she has anything to prove.
"I don't care what people think and say or do," Wozniacki said. "I care about what I know best. I go out there, and what I care about is that I give 100 percent every time."
As does Williams, who looks as close to fully healthy as she's been in more than a year, after a series of setbacks that stemmed from stepping on broken glass at a restaurant last summer. Williams is seeded 28th but playing at a much higher level, which made it all the more surprising that Pavlyuchenkova broke Williams' serve three straight times to start the match.
But Williams broke back each time and the players held serve until the final game of the set, when Williams chased down two balls that were barely within reach to keep the ball in play and finally force an error on set point.
Williams pumped her fist, bent down and shouted "Yes! Yes!"
"For me, it was a slow start, and once I lost serve, I was determined to break serve so I wouldn't be down a break," Williams said. "Then I just kept losing serve in the beginning. Very weird."
The second set was much easier and reversed a pattern that had developed. Williams' last two opponents gave her a much tougher test in the second set than the first.
"If you're going to go out and be nervous and you've got to play Serena, you don't have a lot of chances," Pavlyuchenkova said. "You have to go out and play from the start, do the right things. You can't go out and hope the first few games help you handle your nerves."
Instead, Pavlyuchenkova wilted in the second set and Williams made it through her fifth match without dropping a set. She has lost one or no games in six of those.
"She's playing great," Wozniacki said. "I think she's in great shape. She's been proving that she's back on fire."
Wozniacki's match was originally scheduled for Louis Armstrong Stadium, but got moved to a more intimate setting -- Court 13, capacity 584, after the stadium was deemed unplayable because of damage caused by the rain.
"It actually reminded me of juniors, to be honest," Wozniacki said, echoing the same thought Roddick had shared earlier.
The court, however, is the same size everywhere and nobody covers it better than Wozniacki.
It was a typical match for the 21-year-old from Denmark -- lots of long rallies, not a lot of winners (9) and not many mistakes (25). Wozniacki missed a chance to close it out while serving at 5-3 in the second set. Petkovic pushed it to a tiebreaker, but committed five of her 44 unforced errors during the breaker to lose 7-5.
"If Serena plays well, it's tough to beat her," Petkovic said when asked to handicap the semifinal. "Anybody will lose against her if she's on fire. But if Serena struggles a little bit and Caroline plays consistent, she definitely has her chances."
The winner will play either Stosur or Kerber.
Stosur defeated second-seeded Vera Zvonareva 6-3, 6-3 to improve to 8-2 lifetime against last year's runner-up. Stosur had been involved in two matches that lasted more than 2½ hours, and said she welcomed the two-day break she got because of the rain.
"To do it against a player like Vera who is obviously a quality opponent is, yeah, definitely a good feeling," Stosur said.
Kerber is ranked 92nd and finds herself a match away from playing in the final. In her first career quarterfinal, the German defeated 26th-seeded Flavia Pennetta 6-4, 4-6, 6-3. Pennetta knocked third-seeded Maria Sharapova out of the tournament last week in an upset that turned her side of the bracket into a wide-open affair.
Williams and Wozniacki, however, have not veered from their collision course -- the multi-time champion against the player looking for a Grand Slam breakthrough.
"I know I'm going out there and playing a great champion," Wozniacki said. "She hasn't won 13 Grand Slams for nothing. She's been out there on the big stage many times."