Radwanska knocks out French Open champion in quarter-finals
Victoria Azarenka and Maria Sharapova both had to go three sets to reach the semi-finals of the WTA Porsche Grand Prix in Stuttgart.
Top seed Azarenka needed just shy of three hours on court to see off German wildcard Mona Barthel 6-4 6-7 (3-7) 7-5.
The local favourite hammered down 13 aces but also served up 16 double faults, the last of them coming on her opponent's second match point in the 12th game of the third set.
Azarenka will now face fourth-seeded Agnieska Radwanska, the Pole having seen off reigning French Open champion Li Na of China 3-6 6-2 6-3.
"She (Barthel) keeps producing some great tennis and she showed again today why she is a tough one to beat," said Azarenka.
"Her serve is definitely up there with the best, after more than two-and-a-half hours she was still blasting down aces. I have been saying for a while she is one to watch."
Battled back
Sharapova was on court even longer against Sam Stosur, the second seed having to battle back after losing the first set to clinch a 6-7 (5-7) 7-6 (7-4) 7-5 victory after three hours, one minute.
Stosur actually served for the match at 5-4 in the second but couldn't finish off the Russian.
"She has a great serve and she served as well as she ever has against me," she said afterwards.
"It was pretty difficult to play against her, so I am very happy with the win. It's not over until the last point has been played and you've shaken hands.
"She had her chances to win, so I am just happy to have reached the last four. I have a second chance now and I intend to use it."
Next up for Sharapova will be Petra Kvitova, the third seed having no such issues in her quarter-final as she swept aside German Angelique Kerber 6-4 6-4.
