Maria Sharapova showed improved form as she beat Italy's Karin Knapp in the third round of the French Open.
The Russian top seed had been far from convincing in her opening two matches, with the serve particularly poor.
But after a tight first set, Sharapova enjoyed a 7-6 (7-4) 6-0 victory on Court Philippe Chatrier to set up a last-16 clash with Dinara Safina.
Third seed Jelena Jankovic and fourth seed Svetlana Kuznetsova also went through to round four.
Sharapova struggled in the early stages against Knapp and failed to serve out the set from 5-3, needing a tie-break to move ahead before dominating the second.
"It was like my twin sister was here, and then Maria actually made her flight and made it for the second set," said Sharapova.
"I definitely became a lot more aggressive and stepped in and didn't give her too many easy balls."
"I definitely think I have a chance. Why not?"
"I have double-faulted numerous amounts of times in my career," she said. "Today was an improvement. It is a lot better - felt more comfortable."
She added: "I kind of forgot what it felt like to finish in two sets even though I still managed to play for two hours out there.
"It was quite scratchy the first two (matches) and I spent a lot more time than I would have liked on the court."
Kuznetsova continued her impressive progress with a comprehensive 6-2 6-1 win over fellow Russian Nadia Petrova in one hour nine minutes.
Former finalist Kuznetsova was always in control against a very below-par Petrova, who needed treatment from the doctor at the end of a poor first set.
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"I was trying not to make unforced errors in the first two or three shots. Not to rush too much.
"I definitely think I have a chance (to win the title). Why not? There are a few players who have a shot to win it and I hope one of them is me."
Kuznetsova goes on to face 16th seed Victoria Azarenka in the last 16, after the 18-year-old Belarussian defeated Schiavone 6-1 6-1.
A former world junior number one, Azarenka has dropped just six games in three matches so far.
"This year I improved a lot my forehand, which was my weakshot before," she said. "Now it's like my weapon, which helps me a lot."
Jankovic completed a 7-5 6-3 win over Dominika Cubulkova.
The Serbian led 7-5 4-2 when darkness forced play to be suspended on Friday, but quickly wrapped things up when the pair resumed on Court One.
"It's hard to make a winner against her so I really had to work hard for my points," said Jankovic.
"It's quite hard when you stop and have to come back the next day; you have to start from the beginning. It was important for me to finish in two sets."
Safina, the 13th seed and a dark horse for the title after some good form recently, saw off Jie Zheng 6-2 7-5.
Seventh seed Elena Dementieva beat Olga Govortsova 6-0 6-4 and will next meet fellow Russian Vera Zvonareva, who defeated Aleksandra Wozniak 6-2 6-2.
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