PARIS - Defending champion and world number one Serena Williams has been knocked out of the French Open by Spain's Garbine Muguruza as the women's tournament was thrown wide open.
The top seed lost 6-2 6-2 in the second round to the world number 35 with her defeat coming just an hour after sister Venus also went out 2-6 6-3 6-4 to Slovak teenager Anna Schmiedlova.
It was the earliest exit for a defending champion at Roland Garros since 2005 when Anastasia Myskina of Russia went out in the first round.
Yesterday's defeat was Serena's worst at a Grand Slam in terms of games won and was only the second time in her career she had been beaten at a major in the round of 64.
The last time that happened was on her debut at the 1998 Australian Open.
It was also just the fourth time the Williams sisters had lost on the same day at a major.
"Nothing worked today," said 17-time major winner Serena, who hit just eight winners and a huge 29 unforced errors with five doubled faults.
"I just couldn't serve. But you can't be on form every day. I hate to be off at a Grand Slam but it happens, it's not the end of the world."
Muguruza immediately won praise for her performance.
"Shocker at the French - Serena loses to Garbine Muguruza. Garbine is here to stay, that's for sure, quite a talent," tweeted Martina Navratilova.
The young Spaniard was over-joyed by her performance.
"Today's a great day," she said.
Serena'a defeat was good news for Maria Sharapova who is now the overwhelming title favourite with second seed Li Na having been knocked out in the first round on Tuesday.
The Williams sisters had been scheduled to meet in the third round.
Instead the tournament will get Muguruza against Schmiedlova, the 19-year-old Slovak who ended 32-year-old Venus's 17th French Open.
"It's the biggest win of my career," said world number 56 Schmiedlova who had lost to Venus in straight sets in Miami this season.
"I have big respect for her. She's a great player and I still cannot believe I won."
Defeat for Venus, the 29th seed, meant she has now failed to get beyond the second round in Paris on her last three visits.
She was undone by 47 unforced errors on a half-full Philippe Chatrier court and despite saving two match points it was all too much for mother Oracene who was caught on TV napping as Venus slipped to defeat.
"I think she's very good already, and she's going to be even better as she continues to play. I see wonderful things for her," said Venus of her opponent.
Later on Wednesday, Maria Sharapova, the seventh seeded 2012 champion, faces Bulgaria's Tsvetana Pironkova, a Wimbledon semi-finalist in 2010.