Ivanovic had been hoping to reach her first final of 2010
Kim Clijsters made it through to the final of the Cincinnati Open in unsatisfactory circumstances as Ana Ivanovic retired from their semi-final.
The Serbian was trailing 2-1 after 12 minutes when she made a return and appeared to hurt her ankle.
After receiving extensive treatment Ivanovic returned to the court but was clearly in pain and had to retire.
Clijsters will play Maria Sharapova after the Russian beat compatriot Anastasia Pavlyuchenkova 6-4 3-6 6-2.
Ivanovic is a former world number one and French Open champion but has slipped to 62 in the world following injuries and poor form.
Her run in Cincinnati had suggested that the 22-year-old's form was returning, making Saturday's retirement all the more disappointing.
"Just on that one forehand when I went to step around it, I just felt like pain all of a sudden, so much pain in my foot and I couldn't step on it any more," said Ivanovic.
"All of a sudden on that one shot I felt something crack a little bit. I was very scared.
"I tried bit of tape, but I could not put any weight on it and there was no point in me continuing."
Clijsters, the fourth seed, said: "She is doing well again and then something like this happens, I hope she is OK and it is nothing too serious and she will be OK for the US Open."
In contrast to the Belgian's easy passage to the final, Sharapova was made to battle hard against Pavlyuchenkova.
The three-time Grand Slam winner never truly dominated her determined 19-year-old opponent until she broke in the third set to take a 4-2 lead.
Beaten in the Stanford final by Victoria Azarenka earlier this month, Sharapova said she was now fired up to claim a title ahead of the US Open, which begins on 30 August.
Sharapova has hit form ahead of the US Open
"I certainly want to give it all I have, all the energy and power and everything," said the 23-year-old.
She has not played Clijsters since the Belgian returned last year at the Cincinnati event following a two-year break from the sport.
"I'm excited, it's been a while since we played and we have been through different things in our lives," said Sharapova, referring to her lengthy absence with a shoulder injury.
Pavlyuchenkova, who has been playing doubles in Cincinnati, had a trainer work on her right arm for 10 minutes after the third game.
She admitted: "I was just getting tired. I've played a lot of tennis and had tough matches here."