STANFORD, Calif. -- Dominika Cibulkova wants to think less and win more.
The 24-year-old Slovak has been working on her mental approach and needed to regroup Friday before taking charge in a 7-5, 6-3 victory over Urszula Radwanska in the Bank of the West quarterfinals.
"When things get tight, I start to think more," the third-seeded Cibulkova said.
Cibulkova won her first four games and was ahead 5-1 when No. 7 Radwanska made a run to tie it at 5.
"I wanted to be more active because she likes to wait for mistakes," Cibulkova said. "I was trying to play fast on the baseline. I started going down the line more in the second set. When I'm playing well the fast court is good for me."
The quick pace wasn't as compatible for Radwanska, who pulled a muscle just above her right ankle and needed to be taped to finish the match.
"I couldn't move that well in the second set," she said. "When it was 2-1, I suddenly felt the pain and couldn't go on."
Radwanska said she still expects to play at the Southern California Open, which begins Monday in Carlsbad.
Cibulkova's fast start caught Radwanska off-guard.
"Until it was 5-1 she was playing amazing," Radwanska said. "She didn't miss anything. That's when I started to read her game."
Cibulkova, who has played at the event the past six years, reaching the semifinal two years ago, will face fifth-seeded Sorana Cirstea, a 6-3, 6-3 winner over Olga Govortsova.
Fourth-seeded Jamie Hampton also advanced, beating qualifier Vera Dushevina 6-4, 6-3. She will face top-seeded Agnieszka Radwanska, who beat sixth-seeded Varvara Lepchenko, 7-6 (2), 3-6, 6-3, in a match that lasted well over two hours.
"I lost the last time we played and I was cautious coming in," Hampton said about Dushevina. "I tried to break down her forehand more this time, instead of her backhand. I also served better."
Hampton, who lives in Auburn, Ala., is making her main draw debut in the event, and said she always wanted to attend Stanford.
"In the fifth grade me and my best friend decided we were going to go to Stanford, be roommates and be on the tennis team," Hampton said. "I was going to study medicine. Before turning pro, Florida and Stanford were my top two choices. I verbally committed to Florida because it was closer to home."