Caroline Wozniacki cements grip on world No 1 spot

The 20-year-old Dane reached the top ranking for the first time in her career earlier this month and ensured she would hold onto it at season's end with her 3-6, 6-1, 6-1 win over Schiavone.

The victory also ensured Wozniacki would join Sam Stosur, who beat her on Wednesday, in the semi-finals of the end-of-season tournament. "This has been the most amazing year in my career during which I realised my dream of becoming world number one," Wozniacki said.

"Capturing the year-end world number one ranking is a huge accomplishment for me and I am thrilled that all the hard work has paid off."

Fifth seed Stosur earlier booked her place in the last four despite losing to Elena Dementieva 4-6, 6-4, 7-6 (7/4). The Australian won her opening two matches against Schiavone and Wozniacki to ensure the set she picked up was at least enough to send her through.

For Dementieva it was a morale-boosting win after she had been a set and a break behind. "It wasn't easy to play today after losing to Caroline very easily, but I just tried to improve and be ready for today," the Russian said.

Meanwhile, third-seeded Nicolas Almagro, number four seed Marcos Baghdatis and eighth seed Juan Ignacio Chela reached the quarter-finals of the Bank Austria Trophy in Vienna. Michael Berrer of Germany and Andreas Haider-Maurer of Austria also made it to the last eight.

Almagro defeated Colombia's Santiago Giraldo 7-6, 6-7, 6-3 to reach his eighth quarter-final of the season. The 16th-ranked Spaniard failed to serve out the match at 5-4 in the second set but dominated the decider.

"It was a tough fight and I certainly have to play better in the quarter-finals," Almagro said.

Almagro, seeking his third title of the year, next plays Chela of Argentina, who rallied to beat Slovenian qualifier Grega Zemlja 2-6, 7-6, 6-3.

Baghdatis went 5-4 down against Germany's Bjorn Phau before winning seven straight games to take the opening set and a 4-0 lead in the second.

The 20th-ranked Cypriot, who lost the final in Moscow last Sunday, now faces Berrer after the German beat Pablo Cuevas of Uruguay 5-7, 6-3, 6-3.