Maria Sharapova withdrew 20 minutes before her semi-final match against Nadia Petrova at the East West Bank Classic on Saturday because of a lower left leg strain.
Petrova advanced to yesterday's final against Ana Ivanovic, who rallied from a 4-1 third-set deficit to defeat fellow Serb Jelena Jankovic 4-6, 6-3, 7-5 in the other semi-final.
Sharapova, the top seed, was coming off her first title of the year at last week's Acura Classic in California.
"I can function sitting on my butt and talking, I'm fine," she said. "But running around on the tennis court, no."
Sharapova said the injury occurred on Saturday afternoon on the practice court.
"I could not lift my foot up on the serve and I could not run to more than two or three balls," she said. "It is just so weird how it came on."
She tried various treatments -- including deep tissue massage, an ice bath, acupuncture and taking anti-inflammatories -- in an attempt to play.
"The doctor has seen these things before and was not optimistic," Sharapova said. "You still try and do everything you can. Based on my experience, you never know, but I hope it is only a couple of days."
Sharapova had already withdrawn from next week's tournament in Toronto.
She went on court and apologized to fans waiting for her match to start at Home Depot Center.
No. 4 seed Petrova, who was 1-5 against Sharapova in her career, reached her first final in seven appearances in Carson.
"It's always good to be in the final, but it's always good to make your way through by playing," she said. "It's quite disappointing. I had 15 people coming to watch me. They drove all the way from San Diego."
By reaching the final, Ivanovic will rise to a career-high ranking of fourth, dislodging Svetlana Kuznetsova in next week's WTA Tour rankings.
Ranked fifth this week, Ivanovic will be seeking her second title of the season. The 19-year-old was runner-up at the French Open and a semi-finalist at Wimbledon.
Jankovic, last year's runner-up, was the only semi-finalist with multiple titles this year, winning four. She led 4-1 in the third set and had a break point to go up 5-1, but she sent a backhand wide to give Ivanovic the game.
"I never give up, so I tried to focus on each point and take time for my serve," Ivanovic said. "I got motivated, the crowd helped me a lot with that. They were giving me confidence and fighting spirit."
That helped Ivanovic win three consecutive games to tie the set at 4-all. The second-seeded Jankovic held for a 5-4 lead and had two match points in the next game.
"I had some chances, but at the end she made big serves," Jankovic said. "I was a little bit tired and didn't move my feet at all. I was out of gas."
Ivanovic came up with some big shots under pressure, including a drop volley winner on the first match point and then a forehand winner into the open court on the second match point for deuce.
Ivanovic hit two forehand winners in a row to tie the set at 5-all.
"I believe she was tired," Ivanovic said. "I was on the edge of my energy, but I tried not to think much about that."
Ivanovic, the third seed, was pushed to three sets for the first time in four matches this week.