Maria Sharapova loses but Serena Williams survives at French Open

Lucie Safarova has not previously progressed past the last 16 of the French Open

Defending champion Maria Sharapova was knocked out of the French Open while top seed Serena Williams survived a big scare to reach the quarter-finals.

Russia's Sharapova, who had reached the final for the previous three years, was beaten 7-6 (7-3) 6-4 by Czech 13th seed Lucie Safarova in the fourth round.

Williams, 33, lost the first set to fellow American Sloane Stephens but fought back to win 1-6 7-5 6-3.

She will face 17th seed Sara Errani of Italy for a place in the semi-finals.

Wimbledon champion Petra Kvitova was also knocked out as she lost 6-2 0-6 3-6 to Timea Bacsinszky.

Safarova, 28, will take on Garbine Muguruza in the last eight after the Spaniard beat Italy's Flavia Pennetta 6-3 6-4.

"Maria is an amazing player. I needed to play aggressive and to come forward for the points," said Safarova.

It is second seed Sharapova's earliest defeat at Roland Garros since 2010.

"I felt I had small openings but I wasn't able to play a few good points and Lucie was a much more aggressive player," said Sharapova, who has been fighting a cold.

"My opponent was at a much higher level, more consistent than I was, and that resulted in a bad day at the office."

Williams has been taken to three sets in her last three matches

Stephens, who knocked out Serena's older sister Venus in the first round, secured the opening set in 23 minutes.

Williams made 15 unforced errors and was broken three times by the world number 40.

But the 19-time Grand Slam champion, a winner in 2002 and 2013 at Roland Garros, edged back into the match.

Williams won the second set and took her 22-year-old opponent into a deciding set, where her experience proved vital in clinching her place in the last eight.

"I keep fighting, I never give up," said Williams.

Stephens was seeking to reach the French Open quarter-finals for the first time