Something old, something new in women's semis

Something old and something new distinguish the women's semi-finals at the US Open on Friday when young and seasoned rivalries will determine combatants for the singles crown.

Champion Serena Williams and comeback mum Kim Clijsters, who first met on court at Flushing Meadows 10 years ago, open the final-four matches, followed by a clash of 19-year-olds Caroline Wozniacki of Denmark and Belgian Yanina Wickmayer.

Williams, who won her maiden contest against Clijsters as a 17-year-old on her way to winning the 1999 Open, leads the series 7-1.

Remarkably, they have not met in more than six years, and Williams said Clijsters was more dangerous than ever.

"She has absolutely nothing to lose," second seed Williams said about the 26-year-old Belgian's fast climb back to Grand Slam contention after a mere month back in competition.

"I think that's when you can play your ultimate best."

Clijsters, with 18-month-old daughter Jada along for her first Grand Slam ride since the 2007 Australian Open, said she would turn counter-puncher against big-hitting Williams.

"I think the one who keeps the unforced errors down is going to get through. She's obviously someone who plays with a lot of power, and is still a great mover," said Clijsters.

"Every player always has a moment in a match where, whether it's either one or two games, where they just kind of lose that aggressiveness a little bit or just lose focus.

"You really have to try to just step it up when you feel that things are really like twisting your way a little bit."

Clijsters, the 2005 champion, beat 2007 Wimbledon runner-up Marion Bartoli and seven-times Grand Slam singles winner Venus Williams, but needed three sets to do it.

Williams has breezed through without the loss of a set, using her big serve to set the tone, which she underlined by wearing a T-shirt reading, "Serving Up Some Hot Damn," after her quarter-final win over Italian Flavia Pennetta.

"It means what it means," she said by way of explanation. "Just serving up some hot stuff."

Wozniacki, who has three tournament wins this year including victory in the New Haven run-up event for the Open, warmed up for her first Grand Slam semi with two huge wins.

The Dane ousted former Open winner and Roland Garros champion Svetlana Kuznetsova in the fourth round before sending tournament Cinderella Melanie Oudin home in the quarters.

"I'm thinking well on the court. I think that I make the right decisions. I think that I'm a fighter. I run well, but I'm also capable of changing the rhythm, be aggressive," Wozniacki said in a thumb-nail appraisal of her game.

"I think I'm an all around player.

Wickmayer and eighth-ranked Wozniacki may not be well known to most of the National Tennis Centre crowd but they have known each other since their pre-teen tennis days.

"I know her really well from the juniors and we've played each other growing up," Wozniacki said about the unseeded Belgian. "I think we met each other when we were we were both under-12. That's many years back."

Wickmayer, ranked 50th, flew through the top quarter of the draw under the radar, beating the only seed she faced, 16th-seeded Virginie Razzano of France, in the first round.

Her fourth-round victim, Petra Kvitova of Czech Republic, eliminated top-seeded world number one Dinara Safina.

"I'm really playing under a lot of confidence. Before this my best (Grand Slam) result was second round," Wickmayer said.

"So of course when you get to the third, fourth round, you start surprising yourself. But actually, I've been staying pretty calm. I've worked really hard for this."

Wickmayer said she most admired Clijsters, who could be standing across the net from her in Saturday night's final.

"Let's hope," she said. "Let's all hope we can meet each other in the final.

"But let's be honest. We both have a really tough match in front of us. She has Serena in front of her which is going to be a great match and I'm really excited to see that one."