Three Russian women played their way into the Pilot Pen semifinals, while top-seeded Caroline Wozniacki advanced Thursday without ever taking the court.
Wozniacki's opponent in the quarterfinals, Italy's Flavia Pennetta, withdrew from the tournament with an injury to her right foot.
The Danish star will play Elena Dementieva on Friday. The fourth-seeded Russian needed almost three hours to beat Marion Bartoli of France 6-3, 3-6, 6-2. It was her second consecutive three-hour match after beating Kateryna Bondarenko on Wednesday 7-6 (4), 6-7 (5), 6-4.
"Sometimes you have to go through such a difficult match, very long three sets, to feel your game, to feel your confidence," she said.
In an all-Russian quarterfinal, Maria Kirilenko beat Dinara Safina in straight sets, 6-3, 6-3. Kirilenko said she's not surprised so many Russians are doing so well on the Tour.
"We work a lot," she said. "That's why I think we have good results, you know. Because to have a talent, it's not enough. You have to be patient. You have to work a lot. You have to fight. Everything together. So I think that's why we have so many Russians."
She will play Nadia Petrova on Friday, who also advanced in straight sets, 6-2, 6-1 over Australian Samantha Stosur. Petrova had four aces and won 82 percent of her first-serve points.
"I got a lot of free points with (my serve)," she said. "I just really tried to stay consistent with the returns. My goal was to have a good power behind the ball and also be consistent with my shots, not to give too many free points."
In the first men's quarterfinal match, Thiemo de Bakker of the Netherlands beat Evgeny Korolev of Kazakhstan, 6-4, 6-2.
The other men's quarterfinals, including a match between top-seed Marcos Baghdatis and Sergiy Stakhovsky of Ukraine, were scheduled for later Thursday.