Sam Stosur edged the defending champion. Petra Kvitova and Li Na also made the quarterfinals.
WTA Staff

STUTTGART, Germany - Three of the best clay court players in the game battled into the quarterfinals of the Porsche Tennis Grand Prix on Thursday, with Petra Kvitova, Sam Stosur and Li Na all winning their second rounds.

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The No.3-seeded Kvitova had won a tight two-setter against Francesca Schiavone in Fed Cup play over the weekend, but this time there was nothing tight about it as she won the last five games of both sets to roll to a 62 62 win in 59 minutes. The Czech has now won 26 straight matches on indoor courts.

"I was actually surprised with my serve today - it was one of my best serving days," Kvitova said. "I prefer to play on quicker surfaces, but I feel at home here in the Porsche Arena. The surface is similar to the one at the French Open and it helps more aggressive players, unlike many of the outdoor clay courts.

"I was really sorry at having to withdraw from Stuttgart last year because of an injury, so it's nice everything has started so well for me here this year."

Kvitova won the Premier-level clay court title in Madrid last year and was one of the favorites for the French Open title, before being stopped in a close fourth round encounter with Li Na - speaking of Li, the No.8 seed and defending French Open champion also advanced in Stuttgart on Thursday, getting one break per set and ending the run of lucky loser Akgul Amanmuradova, 64 64.

"Even though her ranking isn't too high right now, Akgul has played many good matches over the years, so I knew I had to play well," Li said. "I liked how I was hitting the ball and fighting for every point out on the court today."

A day earlier, Amanmuradova stepped in after Daniela Hantuchova's withdrawal and stunned World No.16 Dominika Cibulkova in the first round, her third Top 20 win (following wins over Agnes Szavay and Jelena Jankovic).

No.5-seeded former French Open finalist Sam Stosur followed Kvitova and Li into the quarterfinals with a 62 26 63 win over Julia Goerges. Goerges had won the Porsche Tennis Grand Prix last year, taking out Stosur in the semifinals - in fact she had won both of their previous meetings - but after losing the second set this time, Stosur got the lone break of the third and moved safely through.

"It was a tough draw for both of us, but I'm obviously happy to come through," Stosur said. "There are definitely a bunch of players out there I've never beaten before, but you have to believe the next time you go out there you'll be able to change something, play better and win. The first time we played she beat me in straight sets, then our second one here last year was a three-setter...

"I always thought I'd be in with a shot this time."

"I'm pretty satisfied with my performance today, her serve was just better than mine - she got the one break in the third, and that was the difference," Goerges said. "I didn't expect to win this tournament again to be honest, because all the Top 8 players were here, and also it was my first time defending such a big title. But I gave 100% today and I think this match actually helped me."

In the only other match of the day session another German fared much better, as Mona Barthel blasted seven aces to pull off a 63 61 upset over No.7 seed Marion Bartoli. Barthel had two Top 20 wins - against Jankovic and Ana Ivanovic - but had never beaten a Top 10 player before beating the World No.7.

"It was one of the best matches of my life," Barthel said. "I was immediately able to put her serve under pressure and it was enormously helpful being able to play in front of such a fantastic crowd in this arena. Thank you to the fans.

"It's great to have my first win over a Top 10 player. It's something special."