TORONTO (AP) _ Defending champion Amelie Mauresmo of France made the semifinals of the $1.3 million Rogers Cup when Russian Nadia Petrova withdrew due to an injured right chest muscle in their rain-delayed quarterfinal match Friday night.
Mauresmo and Petrova were tied 4-4 in the first set when they headed to the locker-room as a driving rain began to pelt the court.
"At that time I was thinking, `It's going to come,' "Mauresmo said of the time leading up to the storm. ``There's no way this is going to stay like this for all the match. But you just have to try to go off the court in the best position you can.''
Mauresmo, the defending champion, eventually advanced to the semifinals after Petrova withdrew due to a strained right pectoral muscle.
Petrova called for a trainer after losing the first game of the third set and received treatment on the injury. She played one more game before informing the chair umpire she could no longer continue.
When the two players returned after four hours, Mauresmo struggled a bit to find her game as Petrova broke her then held serve for a 6-4 first-set victory. But the defending champion battled from a break down to take the second set 7-5 and was leading 2-0 when Petrova withdrew.
``I think I was able to step up and really play better and better as the match was going,'' Mauresmo said. ``I didn't think I was playing bad. But she was very solid, didn't give me any free points, and I was going for things and missed a few shots here and there that made the difference.
``In these kinds of matches, it's just two or three points that can make the difference in one set.''
In Saturday's semifinals, Mauresmo will play No. 4 Justine Henin-Hardenne of Belgium, who struggled in a 7-5, 7-6 (4) win over Czech teen Nicole Vaidisova in the evening quarterfinal.
Henin-Hardenne appeared to be headed for an easy victory when she took a 4-0 lead in the first set. But Vaidisova proved to be a stiff challenge for the veteran, who made several uncharacteristic errors and wild mishits and struggled with her serve.
Anastasia Myskina defeated Argentina's Gisela Dulko 6-4, 7-5 despite a splint on her sprained left ankle and advanced to the semifinals.
Myskina, seeded ninth, will meet Kim Clijsters, the seventh-seeded Belgian who routed Flavia Pennetta of Italy 6-0, 6-1.
Myskina turned her ankle during the second set Thursday. The Russian hobbled to the sidelines in tears in her match against Shinobu Asagoe, had her ankle taped and returned to win 7-6 (5), 7-5. Myskina underwent treatment late into Thursday night, with more therapy Friday morning.
``Some moves it really bothers me, but some of them were OK,'' Myskina said. ``I didn't really think that Gisela played really smart with me today, so that was big advantage for me. Definitely, the drop shot was the key, but she didn't use it.''
Dulko broke serve to tie it 4-4 in the second set and then held to take the lead. Myskina responded by winning three straight games for the victory.
``My coach even said that I played well,'' Myskina said. ``That's really new. I'm really happy with that.''
Dulko, ranked 35th, defeated third-seeded Svetlana Kuznetsova in the third round. Kuznetsova, the defending U.S. Open champion, hurt her back in the first set.
The first two quarterfinals were completed shortly before a spectacular thunderstorm interrupted the Mauresmo-Petrova match. The storm brought torrential rain that flooded the courts.