By BETH HARRIS
CARSON, Calif. (AP) -- 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.
Playing her first tournament since losing in the semifinals at Wimbledon, Sharapova made numerous errors that allowed the 34th-ranked Chakvetadze to prolong her upset bid.
Sharapova said she played in pain from an inflamed right pectoral muscle that affected her ability to serve hard and pound forehands.
"It wasn't me out there today,'' she said. "I'm serving 93 miles per hour and not hitting my forehand. With that, it's tough to come out against a player that has nothing to lose.''
Sharapova said she first injured the muscle in October in Zurich, playing with heavier balls.
"Since then, it's been an on and off problem for me,'' she said. "I don't think the pain is going to go away with me trying to play and hit as hard as I can.''
She had an MRI on Wednesday that showed the muscle is inflamed, not torn. She taped it for the match, and planned to seek treatment Thursday night.
Sharapova is trying to take over the No. 1 world ranking from Lindsay Davenport, the defending champion who is out with a back injury. Sharapova trails Davenport by 23 points and could become the first Russian to be No. 1 depending on her results this week.
Also bothered by a sore throat and cold, Sharapova didn't rule out withdrawing, depending on how she feels Friday. The tournament has been hard hit by the injury withdrawals of Davenport, Serena Williams, Mary Pierce, Vera Zvonareva, Elena Likhovtseva and Ai Sugiyama.
"There's no pressure at all,'' she said. "It's not important for me to play.''
She needed a tiebreaker to beat Russian compatriot Maria Kirilenko 7-6 (7), 6-2 in her opening match Tuesday.
This time, Sharapova dropped the first set and was tied 4-4 in the second. She held serve, then broke to win the second set when Chakvetadze pulled a backhand wide.
Chakvetadze required a medical timeout in the third set to treat a left groin strain. Three games later, she slipped and fell, but got up and finished the match.
"I pulled my muscle in my leg, so I didn't feel so well,'' she said. "I was really upset because I felt I could win. I had a little bit bad luck.''
Sharapova was broken to open the final set, then blew double break point to trail 2-0. Tied 4-all, Sharapova won three of the last four games, hitting a forehand volley winner on match point, to end the 2-hour, 18-minute match.
"Without playing great, without having a forehand or a serve, you win,'' Sharapova said. "The bad thing is I can't really hit a big serve and you feel like crap.''
Third-seeded Elena Dementieva beat No. 17 Marion Bartoli of France 6-3, 7-6 (4). No. 9 Daniela Hantuchova of Slovakia advanced with a 6-4, 6-4 victory over Kateryna Bondarenko of Ukraine.
Hantuchova will play Sharapova in Friday's quarterfinals. A victory by Sharapova would move the 18-year-old Russian into the top spot in the world rankings.
In other matches, fourth-seeded Nadia Petrova beat No. 15 Klara Koukalova of the Czech Republic 6-2, 6-4; No. 5 Kim Clijsters defeated No. 12 Dinara Safina of Russia 6-0, 7-5; No. 13 Francesca Schiavone of Italy got by Varvara Lepchenko of Uzbekistan 6-3, 2-6, 6-3; and Italian Tatiana Garbin defeated American Lisa Raymond 6-4, 6-3.
Conchita Martinez of Spain advanced to the quarterfinals when Eleni Daniilidou of Greece retired because of a sprained left ankle after losing the first set 6-1.
After rolling through the first set against Safina, Clijsters was broken twice in the second. She needed three match points before Safina's forehand error ended the match.
"Maybe it was going too easy for me,'' Clijsters said. "I hung in there and I ended well, that's the most important thing.''
Two years ago in Carson, Clijsters became the world's top-ranked player. Injuries sidelined her for much of last year, but she has won three titles so far this year.