MASON, Ohio (AP) Fifteenth-seeded Nadia Petrova became the third seeded player to be eliminated from the $2 million Cincinnati Women's Open when mid-90 degree heat forced her to retire from her match while trailing against Christina McHale on Tuesday.

McHale won the first set 7-6 (4) and was leading 5-3 in the second when the 21st-ranked Petrova retired because of heat illness. She became the second player to retire because of the heat. Olga Govortsova retired against 13th-seeded Sasha Peer on Monday.

McHale, ranked 132nd, was surprised to see Petrova retire.

I'm not really sure what happened,'' said the American, whose biggest career win came at Charleston, S.C., in April when then-No. 9 Victoria Azarenka was forced to retire from their match.I know she called the trainer, but I wasn't sure what she called the trainer for. I didn't try to focus too much on that. I'm just excited to move on to the next round.''

McHale is scheduled to meet qualifier Ayumi Morita in the second round.

Every singles match in the day session lasted the minimum two sets. Sixteenth-seeded Marion Bartolo beat Alona Bondarenko 7-6 (4), 6-1 to reach the third round, while 12th-seeded Yanina Wickmayer advanced to the second round with a 6-2, 6-2 win over Greta Arn and 11th-seeded Flavia Pennetta rolled to a 6-4, 6-1 win over Jie Zheng.

In other first-round matches, Sylbille Bammer beat Sorana Cirstea 7-6 (5), 6-2, Elena Vesnina eliminated Melanie Oudin, 6-2, 6-3, Anastasia Pavlyuchenkova ousted Daniela Hantuchova 6-3, 6-1 and Maria Kirilenko cruised past Kateryna Bondarenko 6-1, 6-3.

Also, Andrea Petkovic knocked off Coco Vandeweghe 7-6 (1), 6-1, and No. 46 Gisela Dulko upset 26th-ranked Lucie Safarova 6-4, 6-3.

The 42nd-ranked Oudin, who reached the quarterfinals of the U.S. Open last year at the age of 17, managed just one winner against the 49th-ranked Vesnina.

I saw on the screen after the first set that I have like 10 winners or eight winners or something, and she has not even one, so for me, I was surprised, because I didn't remember that because I was so focused,'' the Russian said.Yeah, maybe today she didn't play her best tennis, but I think I was playing today pretty well, and I was dominating through the whole match and trying to be aggressive.

``I was trying to play smart today, because she's a very smart player. She can read your game and be everywhere on the court, so for me today, the question was to try to be smarter than her.''

Oudin credited Vesnina's aggressiveness.

Today, it was pretty hard for me to hit a winner when she was being so aggressive so quickly,'' the Marietta, Ga., native said.Normally, like when I play, I'm hitting a lot of winners, so that definitely was against me today. It kind of started going so fast and she wasn't missing and I was missing, because then I tried to go for too much. Just wasn't a good day.''