Sam Stosur shocks last year's runner-up with stylish win at French Open

Australian is in fine form on favoured surface

Sam Stosur celebrates victory on Friday

It is six years since Sam Stosur reached the final here at the French Open, but the 32-year-old Australian believes she is playing as well on clay as she has ever done.

Stosur, who beat last year's runner-up, Lucie Safarova, 6-3, 6-7, 7-5 to reach the fourth round, won her only Grand Slam title at the US Open, but this is where she has produced some of her best tennis. As well as reaching the 2010 final, in which she lost to Francesca Schiavone, Stosur has played in two semi-finals here.

Simona Halep, the runner-up here in 2014, will be Stosur’s next opponent, but the Australian is full of confidence. “I can’t remember being so happy to win in the third round,” she said after beating Safarova. “It means a lot.”

Safarova had won 11 of her previous 14 meetings with Stosur, including a clay-court final in Prague last month. Stosur, however, hit the ball consistently well to win a high-quality contest, which was settled when the Australian broke serve in the final game.

Stosur said afterwards that she felt she was playing as well as she had in the 2010 tournament, when she beat Serena Williams en route to the final. “I feel like today was a really good step up again in level,” she said. “That's probably as good as I have played here for many years.”

Halep, nevertheless, dropped only two games in beating Stosur in the Madrid semi-finals earlier this month. The Romanian is through to the last 16 thanks to a 4-6, 6-2, 6-3 win over Japan’s Naomi Osaka, the world No 101. Osaka, aged 18, surprised Halep with the quality of her ground strokes in the opening set before the world No 6 took control.

“I feel like today was a really good step up again in level. That's probably as good as I have played here for many years

&#13; <p>Sam Stosur</p>&#13;

Petra Kvitova joined the list of fallen giants when she was beaten 6-0, 6-7, 6-0 by Shelby Rogers, the world No 108. Kvitova has won Wimbledon twice but has never gone beyond the semi-finals here. Her exit means that four of the top 10 women’s seeds have failed to reach the last 16.

Shelby, a 23-year-old American, is through to the last 16 of a Grand Slam tournament for the first time. “It was incredible,” Shelby said of her moment of victory. “I’m one that cries very easily and I think everyone saw that. I immediately started crying. It’s definitely a little blurry.”

Garbine Muguruza continued her impressive progress, beating Belgium's Yanina Wickmayer 6-3, 6-0. The Spaniard has dropped only five games in her last two matches. “Today was a perfect day,” Muguruza said afterwards. “Everything was easy. You go to warm-up, perfect sun, then you go on court. It gives you energy, it's beautiful.”

Agnieszka Radwanska is also through to the fourth round, but the world No 2 was taken to three sets by the Czech Republic’s Barbora Strycova before winning 6-2, 6-7, 6-2. She next plays Bulgaria’s Tsvetana Pironkova, who beat Sloane Stephens 6-2, 6-1.