Amelie Mauresmo was upset by Czech teenager Nicole Vaidisova and second-seeded Maria Sharapova pulled out with a foot injury Friday, depriving the Kremlin Cup of its top two seeded women.

Vaidisova, seeded eighth, was one game from elimination before she rallied to win 1-6, 7-5, 7-6 (3). It was her second straight victory over Mauresmo _ Vaidisova also won in the fourth round of the French Open.

On Saturday, Vaidisova will play fifth-seeded Russian Nadia Petrova, who advanced to her second straight semifinal with a 7-5, 6-1 win over compatriot Vera Zvonareva. Petrova won the Porsche Grand Prix in Stuttgart, Germany, last weekend _ her fifth title this season _ and has not dropped a set in four matches here.

Mauresmo, looking for her fifth title this season, had little trouble against 17-year-old Vaidisova in the first set and led 5-2 in the second set, but Vaidisova saved two match points while winning the last five games of that set.

``My serve started to go down and I definitely wasn't playing as well as I did in the beginning,'' Mauresmo said.

In the third-set tiebreaker, Mauresmo saved a match point before Vaidisova returned a drop shot with the court wide open.

``I think I just played better in the end and I'm happy about that,'' Vaidisova said.

U.S. Open champion Sharapova, her right foot hurting so much she couldn't walk, withdrew before her quarter-final against Anna Chakvetadze. Sharapova beat Ekaterina Bychkova in straight sets Wednesday.

``I couldn't practice and even walk yesterday,'' she said. ``I have to pull out. I'm really disappointed, but I have no choice.''

In an all-Russian semifinal, Chakvetadze will play fourth-seeded Elena Dementieva, who prevailed on two tiebreakers to beat sixth-seeded Patty Schnyder of Switzerland 7-6 (6), 7-6 (1).

Among the men, top-seeded Nikolay Davydenko defeated Max Mirnyi 6-3, 7-5 and will play seventh-seeded Fabrice Santoro in the semifinals. Santoro scored a 6-3, 7-5 victory over Philipp Kohlschreiber of Germany.

© The Canadian Press, 2007