French Open champion Anastasia Myskina beat Wimbledon winner Maria Sharapova 7-5, 6-2 to go through to the semi-finals of the Acura Classic in California on Friday.
"This means a lot because she's the Wimbledon champion and a great player," third seed Myskina said. "I get a lot of confidence from this match."
Myskina will face Vera Zvonareva in an all-Russian semi-final after the 12th seed received a walkover from Serena Williams, who pulled out of the tournament with inflammation to her left knee.
Fourth seed Lindsay Davenport continued her outstanding play with a 6-1, 6-3 victory over Ai Sugiyama of Japan.
Davenport will face Russian fifth seed Elena Dementieva, who beat American Amy Frazier 6-2, 6-1.
"I'm really proud of myself that I've been able to come back and be at a top level again," said Davenport, who is coming off back-to-back title runs in Stanford and Carson and is on a 12-match winning streak.
In a brilliant performance, the 23-year-old Myskina ably moved Sharapova around the court and rarely allowed her compatriot to dictate play.
Sharapova, 17, led 5-2 in the first set but then rapidly lost control of the match when Myskina moved inside the court and began to cut off her angles.
Myskina fought off a set point in the ninth game with a forehand winner down the line. She broke to 6-5 when Sharapova double faulted and held on to win the set when the sixth seed committed a forehand error.
Myskina raced off to a 4-0 lead in the second set. Sharapova staged a brief rally to 4-2 but doubled faulted on break point to fall behind 5-2. Myskina won the contest when Sharapova missed a forehand.
"She played really well and smart at the beginning," Myskina said. "Then I found the rhythm and understood what she was trying to do."
Sharapova was disappointed but said she would gain from the experience and, in time, catch up with Myskina.
"I was trying to find a way though the match but I didn't do anything special," said Sharapova, who produced 45 unforced errors, including six double faults.
"Her level of play went up and when had to pick up my level I didn't. She's older than me and finds a way to win. When I get to her age, I'll be a lot more experienced and stronger.
"As much as I want to win, I know I can learn a lot from my mistakes," added Sharapova, who has accepted a wildcard entry for next week's tournament in Montreal in order to get more matches before the U.S. Open.