Wozniacki reaches quarters; Azarenka pulls out in Beijing

World No. 1 and reigning champion round winners, while second- seeded Victoria Azarenka pulled out of the draw at the $4.5 million China Open tennis event.

The six-time 2011 WTA titlist Wozniacki got past capable Estonian Kaia Kanepi 6-3, 7-6 (7-3) on the hardcourts at the National Tennis Center.

Wozniacki's quarterfinal opponent on Friday will be Italian veteran Flavia Pennetta. The Danish star defeated Russian Vera Zvonareva in last year's Beijing finale.

Azarenka, meanwhile, was scheduled to meet 13th-seeded Anastasia Pavlyuchenkova on Day 6, but the Belarusian star pulled out of the bout, citing a right foot injury. The Russian Pavlyuchenkova received a walkover into the quarters, where she'll encounter ninth-seeded rising German Andrea Petkovic.

Eleventh-seeded Pole Agnieszka Radwanska remained hot with a 6-4, 6-2 spanking of Swede Sofia Arvidsson. Radwanska is fresh off her title last week in Tokyo, where she upset Zvonareva in the final of the Pan Pacific Open.

Also on Thursday, Pennetta outlasted Slovakian Dominika Cibulkova 6-1, 4-6, 6-4, 2005 Beijing titlist Maria Kirilenko drubbed Austrian Tamira Paszek 6-1, 6-2, and Romanian Monica Niculescu overcame French fellow qualifier Virginie Razzano 4-6, 6-1, 6-2.

Friday's other quarters will pit Radwanska against former world No. 1 Ana Ivanovic and Kirilenko versus Niculescu. The Serbian Ivanovic routed Zvonareva here on Wednesday.

The 2011 China Open champ will pocket $775,500.