Maria Sharapova survived an injury and another challenge from a fellow Russian, defeating Anna Chakvetadze 4-6, 6-4, 7-5 Thursday in a third-round match at the JPMorgan Chase Open.

"I'm not playing 100 percent physically," Maria said. "I'm serving 92 miles per hour and I'm not hitting my forehand. With that, it's tough to play a girl, who has nothing to lose, is swinging out there and seems to be playing unbelievable. "The good thing is that I know that at the end of the day without playing great, with having a few problems and a serve, you tough it out and you win. The bad thing is I can't hit a big serve and you feel like crap."

Maria admitted inflammation of her right pectoral muscle has weakened her powerful serve and forehand. She sufferered the injury playing at Zurich last year and required an MRI on Wednesday. "There's nothing torn, thank God, but it keeps coming back," she said. "It's the whole muscle and hurts on the moment of impact. The more you play and the bigger you hit, the more painful it is." "There's no pressure at all," she said. "It's not important for me to play."