TOKYO -- Top-seeded Dane Caroline Wozniacki and former champion Elena Dementieva were among Thursday's quarterfinal winners at the $2 million Toray Pan Pacific Open.
The former U.S. Open runner-up Wozniacki was leading sixth-seeded Agnieszka Radwanska 5-0 in the first set when the Pole retired with a left foot injury.
Wozniacki, who will battle eighth-seeded Belarusian star Victoria Azarenka in Friday's semifinals, could supplant Serena Williams atop the WTA rankings with a title this week and a quarterfinal appearance in Beijing next week.
"If I reach No. 1 that is great," Wozniacki said. "It's always been a goal of mine, but if it doesn't happen this year there will be other chances."
Meanwhile, the seventh-seeded Dementieva captured the marquee match of the day when she took out second-seeded fellow Russian Vera Zvonareva in 7-5, 6-2 fashion on the hardcourts at Ariake Colosseum. Dementieva dismissed Zvonareva in 1 hour, 41 minutes, as Zvonareva piled up nine double faults and had her serve broken a whopping seven times.
Zvonareva was relatively fresh off her runner-up finish at the U.S. Open and also reached the Wimbledon final back in July.
The two-time major runner-up Dementieva, who captured this Tokyo tournament in 2006, will meet fifth-seeded French Open champ Francesca Schiavone in the final four. Dementieva was forced to retire from her semifinal match against Schiavone at Roland Garros because of a calf injury.
Schiavone advanced by outlasting Wimbledon and U.S. Open quarterfinalist Kaia Kanepi of Estonia 7-5, 4-6, 7-5 on Thursday.
The aforementioned Azarenka cruised past American qualifier Coco Vandeweghe 6-2, 6-1 on Day 5 here.
The 2010 Pan Pacific Open champ will earn $350,000.