Injury Downs Petrova, Belgians Advance at WTA Toronto

Petrova trailed 6-4, 5-7, 0-2 at the time of the injury.

"It's unfortunate that the match had to end this way," Petrova said. "I have felt a little soreness and tightness since last week. I think it might be because of the three weeks of not playing matches. Today was very humid outside and the balls were a little heavier. I had to put extra force in my shots."

Mauresmo was one of three former No. 1s advancing into the semis with No. 4 seed Justine Henin-Hardenne (d. Vaidisova), and No. 7 seed Kim Clijsters (d. (14) Pennetta 0-and-1) also posting wins.

"This was a difficult match for me tonight," Henin-Hardenne said. "Nicole played very well -- she played like a Top 10 player tonight. We had a lot of good rallies. I'm happy to win the match."

Also into the semis was struggling No. 9 seed Anastasia Myskina, who defeated Gisela Dulko in straight sets.

"I didn't think that Gisela played smart with me today," said Myskina, hindered by a sprained ankle. "Definitely, the drop shot was the key, but she didn't use it. She didn't really move me around the court. Usually she plays a lot of angles, but not today really...At the beginning of the year, I was losing a lot of easy matches. I was really in bad condition. But now I'm feeling much better."

On tap for the Saturday semifinals are (7) Clijsters vs. (9) Myskina (the Belgian leads the career meetings 6-3), and (2) Mauresmo vs. (4) Henin-Hardenne (tied 3-3).

The doubles semifinals will be (4) Hantuchova/Sugiyama vs. (6) Groenefeld/M.Navratilova, and (8) Asagoe/Garbin vs. (3) Martinez/Ruano Pascual.