Russian fourth seed Elena Dementieva eased into the quarter-finals of the Advanta Championships with a 6-3, 6-4 victory over German qualifier Angelika Bachman at the Philadelphia event on Wednesday.
Dementieva's second round victory over a stubborn but overmatched opponent ensured a seventh quarter-final appearance in her last eight tournaments.
Also advancing was fellow-Russian Nadia Petrova after the sixth-seed defeated qualifier Tatiana Poutchek of Belarus 6-4, 6-2 in a first round match.
The victory earned Petrova a second round encounter against her unseeded compatriot Yaroslava Shvedova.
Dementieva and Petrova represent their nation's best chances of a victory at the event after second-seeded Maria Sharapova pulled out on Tuesday with a thumb injury.
Seventh-seeded Czech prospect Nicole Vaidisova continued her run of good form to edge compatriot Klara Koukalova 4-6, 6-1, 6-4 in their second round match.
With the victory, Vaidisova stretched her winning streak to 17 consecutive matches which includes three title victories in Asia.
In other second-round matches, American Mashona Washington stopped Russian Tatiana Panova 7-6, 6-3 and Slovakia's Martina Sucha defeated American Angela Haynes 6-3, 6-1.
In a first round match, Kveta Peschke of the Czech Republic crushed American Jill Craybas 6-1, 6-1.
The Tier 11 indoor hardcourt event offers $585,000 in prize money and the defending champion Amelie Mauresmo of France opens her campaign on Thursday with a second round match against Japan's Ai Sugiyama.