Maria Sharapova gains semifinal
Sharapova, the defending champion, needed more than 3 hours to overcome Lucie Safarova a day earlier. This one was an hour shorter but perhaps just as intense.
"It was hard to get my body going, I needed some time to warm up a little," Sharapova said. "Another tough one."
Sharapova used this indoor clay-court tournament last year to warm up for the French Open, where she won the title.
Against Ivanovic, another former No. 1 and the 2008 French Open champion, Sharapova squandered a 4-1 lead in the third set before breaking serve again and serving out the match on her second match point.
"Ana has a much bigger game, a big forehand, I really had to push myself through the end, I am glad I got through," the Russian said.
The American next goes against second-seeded Li Na of China, who defeated fifth-seeded Petra Kvitova of the Czech Republic 6-3, 7-5. Li blew a 5-2 lead in the second set but won the last two games of the match, converting her third match point.
"It shows that it is not over until game, set and match," Li said.
Germany's No. 1 player is looking for her first title of the year after finishing runner-up in Monterrey. She reached the semis in Stuttgart for the first time.
Shvedova trailed 4-1 before breaking back. But she dropped her serve again with two errors from the baseline. The two traded breaks in the first three games of the second before Kerber opened a 3-1 lead, only to see Shvedova pull level at 3-3. Kerber raced to a decisive 5-1 lead in the tiebreaker.
"I played my game and I was aggressive," Kerber said.
Ivanovic had one of her seven double-faults to give Sharapova a break point and the Russian attacked the Serb's second serve to force her into an error for a 6-5 lead. Sharapova then served out the first set.
Sharapova then produced one of her six double-faults to give Ivanovic the second set.
The Russian started strongly in the third, before Ivanovic pulled level at 4-4.
"I felt I needed to give myself a little energy after the second set," Sharapova said.
Ivanovic failed to build on her momentum and dropped her serve in the ninth game, before Sharapova clinched the match when Ivanovic hit a forehand wide.
"It's frustrating, I feel I was so close," the Serb said. "It was very close. A few points that could have gone either way decided the match."
"Still, I feel I played high-quality tennis, I feel I can challenge anyone on this surface," Ivanovic said.