Sharapova beats top seed

Defending champion Maria Sharapova finally saw off the challenge of top seed Agnieszka Radwanska on her eighth match point in the quarter-finals of the Porsche Grand Prix.

Sharapova came through 6-4 6-3 in one hour and 39 minutes to extend her winning streak on the indoor clay in Stuttgart to 11 matches.

The Russian edged a first set that started with straight seven breaks and then moved 5-2 up in the second, only to falter with the winning line in sight.

World No 3 Radwanska produced her best tennis in the penultimate game, fighting off six match points to break Sharapova's serve.

But the Pole fell 15-40 down on her own delivery in the next game and Sharapova, after wasting another match point with a wild forehand, clinched victory with a forehand winner into the corner.

World No 9 Sharapova is without a title this year and defeat would have seen her fall out of the top 10.

'Big victory'

"This was a big victory for me, the biggest since my injury," said Sharapova, who returned late last year after missing more than four months following shoulder surgery.

Her semi-final opponent will be eighth seed Sara Errani, who was leading 6-3 6-7 (6/8) 3-0 when Carla Suarez Navarro pulled out of their quarter-final with a hand injury.

On the other side of the draw, ninth seed Ana Ivanovic outlasted 2009 Stuttgart champion Svetlana Kuznetsova 6-3 2-6 6-4.

Ivanovic, who has already won two titles this year, will take on fellow Serb Jelena Jankovic in the last four.

Fifth seed Jankovic beat Russia's Alisa Kleybanova 6-4 6-3.