Injured Wozniacki wins, Serena in semis

Caroline Wozniacki burst into tears after overcoming crippling cramp to edge closer to the WTA Championships semi-finals yesterday as new world number one Serena Williams cruised into the last four.

Wozniacki, 19, defeated Russia's late call-up Vera Zvonareva 6-0, 6-7 (3/7), 6-4 to record her second win in two matches, while 2001 champion Williams made it three wins in three by beating Russia's Elena Dementieva 6-2, 6-4.

Denmark's Wozniacki, the youngest player in the draw, ended her 2hr 48min match sobbing after collapsing to the court in agony, her body wracked by cramp, when she was just two points from victory.

But world number nine Zvonareva, the runner-up in 2008 and who was summoned to the 4.55 million dollar event after Dinara Safina withdrew on Wednesday, failed to take advantage.

Wozniacki, the US Open runner-up and playing in her first season-ender, had led by a set and 5-2 before wasting two match points in the 12th game of the second set.

"In the third set, I just knew I really had to go for it," said world number four Wozniacki.

"When it was 3-1 for me in the final set, I got cramp in my left leg. From there, it just got worse and worse. I have absolutely no idea how I pulled it through, but I'm very happy about it.

"I'm going to do everything I can to get ready for tomorrow (her last group match against Jelena Jankovic where a win will ensure a semi-final spot). I'll drink a lot of fluids, eat some good food, do stretching, get massage, take a salt bath."

The 25-year-old Zvonareva battled impressively, even overcoming a nasty courtside nosebleed in the second set.

For the second consecutive evening, the 10-minute heat rule was invoked after the second set, allowing Wozniacki, who needed three hours to win her opener against Victoria Azarenka, and Zvonareva to recover from the heat and crushing humidity.

On their return, Wozniacki led 3-1, but was pinned back to 3-3 before needing treatment on her bandaged thigh.

But with the tie seemingly slipping away, she bravely broke to lead 5-4 before claiming victory when Zvonareva netted a forehand.

Serena Williams, who made sure of claiming the year-end world number one spot when Safina withdrew, cruised past Dementieva 6-2, 6-4 in the pair's sixth meeting of 2009.

"I'm really happy to be in the semi-final. I have never done well in round-robin play," said Serena.

Other result: V. Williams vs Kuznetsova 6-2, 6-7, 6-4.