April 27 (Reuters) - Top seed and holder Maria Sharapova battled through a tough three-set claycourt match for the third day in a row on Saturday to book a place in the final of the Stuttgart Grand Prix.
The Russian ended the challenge of home favourite Angelique Kerber, beating the third seed 6-3 2-6 7-5 to set up a title showdown with Li Na of China who put out American qualifier Bethanie Mattek-Sands 6-4 6-3.
Sharapova, who was also taken to three sets by Czech Lucie Safarova on Thursday and by Serb Ana Ivanovic 24 hours later, has an excellent record when she is taken the distance.
The world number two had won 28 of her previous 31 three-set encounters and it was the Russian's extra aggression that proved the key against Kerber.
"I'm really happy with the way I fought through the third set," Sharapova told the tour's official website (www.wtatennis.com). "Obviously I'd prefer to win easier but that isn't always the situation you're given.
"I had to play a longer match today and the great thing is I got through. I did my job out there," added Sharapova after winning her 15th straight claycourt match.
Kerber said she would take the positives out of her run to the semi-finals.
"I'm disappointed because it was close and tough today," the German explained. "But I've had a great week.
"I'm feeling good on clay and I will take this experience and look forward to the tournaments coming up."
World number five Li enjoyed a more straightforward passage into the final as she swept past Mattek-Sands in straight sets.