PARIS - Defending champion Maria Sharapova was sent packing from the French Open at the fourth-round stage on Monday, but top seed Serena Williams survived a scare to seal her quarter-final place. Sharapova, seeded two, was beaten in straight sets 7-6 (7/3), 6-4 by Lucie Safarova, the Czech 13th seed who will now meet Garbine Muguruza of Spain in the last eight.

Williams, meanwhile, lost the first set against compatriot Sloane Stephens on the same Court Philippe Chatrier but came back to win 1-6, 7-5, 6-3 and set up a quarter-final with Sara Errani of Italy who beat unseeded German Julia Goerges 6-2, 6-2. Sharapova, , who was looking to become the first woman to successfully defend the French Open title since Justine Henin in 2007, was punished for an erratic display from beginning to end. "I had a few small openings but I wasn't able to keep up my level. She was more consistent and aggressive, created the angles and that was the difference," said Sharapova, who had been battling a heavy cold all week. "It was a tough day at the office."

In contrast, Williams kept alive her hopes of winning a third French Open and a 20th Grand Slam crown, but only after another sluggish opening to her match. Just as against Anna-Lena Friedsam and Victoria Azarenka in the previous two rounds, Williams lost the first set.

The unseeded Stephens beat Venus Williams in the first round and was looking to become the fourth player to defeat both sisters at the same Grand Slam after Martina Hingis, Henin and, most recently, Kim Clijsters at the 2009 US Open. "I feel like I'm living on the edge but, you know, I've got to get off the edge. I dont like to take chances," said Serena after winning three straight matches from a set down at a major for the first time since the 1999 US Open -- a tournament which gave her the first Grand Slam title of her career. "I'm not really happy about my performance. To go three sets back to back to back is verging on unprofessionalism for me." Errani, the Italian 17th seed who was the runner-up in 2012, lies in wait after she Belgian Alison Van Uytvanck is through to a Grand Slam quarter-final for the first time after beating a fellow unseeded player, Romanian Andreea Mitu, 6-1, 6-3. The 21-year-old, ranked 93 in the world, becomes the first Belgian to reach the quarters at Roland Garros since Henin in 2007. Van Uytvanck will meet either fourth-seeded Wimbledon champion Petra Kvitova of the Czech Republic or Switzerland's 23rd seed Timea Bacsinszky, who met later on Monday.