World No. 1 Victoria Azarenka and two-time champion Maria Sharapova were among Wednesday's third-round winners at the $2.17 million Pan Pacific Open tennis event.
The Australian Open champion and U.S. Open runner-up Azarenka dropped 14th- seeded Italian Roberta Vinci 6-4, 6-2, while the second-seeded French Open champion and former No. 1 Sharapova got past 16th-seeded Czech Lucie Safarova 6-2, 7-6 (7-5) in 1 hour, 43 minutes on the hardcourts at Ariake Colosseum.
The Australian Open runner-up and Olympic silver medalist Sharapova needed over three hours to win her second-round match on Tuesday.
"After a long match yesterday I was really happy to win in two sets," Sharapova said. "I had a bit of a letdown in the second set but was really happy that I could close it out in the tiebreaker."
Up next for Azarenka will be fifth-seeded German left-hander Angelique Kerber, while the 2005 and 2009 Pan Pacific titlist Sharapova will meet eighth-seeded Aussie Samantha Stosur in Thursday's quarterfinals. Kerber whipped Pole Urszula Radwanska 6-1, 6-1, while Stosur handled 12th-seeded Slovak Dominika Cibulkova 6-4, 7-5 on Day 4 in Tokyo.
Meanwhile, third-seeded and defending Tokyo titlist Agnieszka Radwanska rolled past American qualifier Jamie Hampton 6-4, 6-3 and surging 10th-seeded Dane Caroline Wozniacki upended seventh-seeded Chinese star Li Na 4-6, 6-3, 6-4. Radwanska beat Russian Vera Zvonareva in last year's finale here. Wozniacki is fresh off her first title of the year last week in Seoul and was a Pan Pacific champion in 2010.
Also on Wednesday, sixth-seeded French Open runner-up Sara Errani of Italy overcame ninth-seeded French slugger Marion Bartoli 3-6, 6-2, 6-2 and 17th-seeded Russian Nadia Petrova doused Croat Petra Martic 7-6 (7-2), 6-7 (1-7), 6-4.
Thursday's other quarters will pit Wimbledon runner-up Agnieszka Radwanska against Wozniacki and Errani versus Petrova.