Top seed Caroline Wozniacki of Denmark moved into the quarter-finals at the Family Circle Cup with a 6-2, 7-5 win over Switzerland's Patty Schnyder on Thursday.
The 19-year-old Dane, who lost in last year's final, will now play Russia's Nadia Petrova, the 2006 winner who earlier eased past Canada's Aleksandra Wozniak 6-2, 6-4.
Wozniacki and Petrova are 1-1 in head-to-head matches with the Danish World No 2 winning their most recent meeting at Indian Wells last month in three sets.
Second seed Jelena Jankovic, who claimed the title in 2007, moved into the last eight with a 6-3, 6-1 victory over Evgeniya Rodina of Russia in their first ever meeting.
The Serb now faces eighth-seed Daniela Hantuchova of Slovakia who needed two hours 44 minutes to overcome German Angelique Kerber 6-7, 7-5, 6-3.
Russia's number seven seed Vera Zvonareva also moved into the third round after cruising past Ukraine's ninth-seeded Alona Bondarenko 6-2, 6-1 in just an hour.