PARIS (AFP) - Defending champion and world number one Serena Williams was knocked out of the French Open by Spain's Garbine Muguruza on Wednesday as the American star stumbled to her second worst Grand Slam defeat.
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 was eliminated in the first round.
With Li Na losing in the first round on Tuesday, Serena's defeat marks the first time in the Open Era that the top two seeds had failed to get to the third round at a major.
Wednesday's defeat was Serena's worst at a Grand Slam in terms of games won and was only the second time 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.
"Nothing worked today," said 17-time major winner Serena who hit just eight winners and a huge 29 unforced errors with five double 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.
"I will have to work five times as hard to make sure it doesn't happen again," added the 32-year-old who suffered her only Grand Slam first round loss in Paris in 2012.
The 20-year-old Muguruza was over-joyed by her performance. "Today's a great day," she said.
Serena's defeat was good news for Maria Sharapova who is now the overwhelming title favourite.
The Russian seventh seed, who was champion in 2012, responded to the challenge by beating Bulgaria's Tsvetana Pironkova 7-5, 6-2.
The Williams sisters had been scheduled to meet in the third round but their back-to-back exits represented just the fourth time they had lost on the same day at a major.
Instead the tournament will get Muguruza against Schmiedlova, the 19-year-old Slovak who ended 32-year-old Venus's 17th French Open with a 2-6, 6-3, 6-4 win.
Schmiedlova was just a month old when the American made her professional debut back in 1994.
"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.
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.
As the American sisters exited, 18-year-old Taylor Townsend gave her country a glimpse of a bright future when the world number 205, making her Grand Slam debut, knocked out French 20th seed Alize Cornet, 6-4, 4-6, 6-4.
Left-hander Townsend held her nerve after squandering a 4-1 lead in the second set and 5-1 advantage in the decider to take victory on a fifth match point with her scintillating brand of tennis yielding 43 winners as well as 55 unforced errors.
"The sky's the limit," said the violin-playing teenager.
The men's tournament was sedate by comparison on Wednesday.
Second seed Novak Djokovic, the 2012 runner-up who needs a French Open title to complete a career Grand Slam, restored order to the tournament with a 6-1, 6-4, 6-2 win over Jeremy Chardy of France to reach the last 32.
Djokovic took his record over the world number 42 to 9-0.
Roger Federer, the 2009 champion and fourth seed, also reached the third round with a 6-3, 6-4, 6-4 win over Argentine qualifier Diego Sebastian Schwartzman.
It was Federer's 60th win at Roland Garros as he goes on to face Russian 31st seed Dmitry Tursunov for a place in the last 16.
Also progressing were Czech sixth seed Tomas Berdych who beat Alexsandr Nedovyesov of Kazakhstan 6-7 (4/7), 6-4, 7-5, 6-3 and Milos Raonic, the eighth-seeded Canadian who defeated Jiri Vesely of the Czech Republic, 7-6 (7/4), 6-4, 6-1.