Defending champion Maria Sharapova crashed out of the French Open after she was beaten in straight sets by Lucie Safarova in the fourth round.
Sharapova has reached three consecutive finals at Roland Garros and won two of those but Safarova pulled off the biggest shock of the tournament so far to win 7-6 (7/3) 6-4.
The Czech has never been past the last 16 before in Paris and she will now play Spain's Garbine Muguruza for a place in the semi-finals.
"I knew Maria is an amazing player and I needed to play aggressively and come forward for the points so I'm really happy," Safarova said after the match.
"I'm so happy, it's amazing, it was a great match today and the crowd were so good."
Safarova had only beaten Sharapova once in five previous meetings but she simply outgunned the world number two, hitting 34 winners to her opponent's 20 and breaking serve three times.
After edging a tight first set in a tie-break, Safarova raced into a 3-0 lead in the second but Sharapova, renowned for her resilience, fought back to level at 3-3.
The momentum appeared to have turned in the Russian's favour, particularly when Safarova missed a chance to go 4-2 up after she blazed a short forehand wide, but the world number 13 regained her composure to lead 5-4.
Sharapova, serving to avoid defeat, saved one match point when Safarova netted another simple forehand, but the Czech made no mistake at the second opportunity, sealing a stunning victory in one hour and 50 minutes.
Serena Williams survived another scare as she was tested to the full by American compatriot Sloane Stephens on court Philippe Chatrier.
With Sharapova tumbling out of the tournament earlier, that should have given Williams extra motivation in the hunt for a third Roland Garros title.
However, the top seed instead struggled to a 1-6 7-5 6-3 fourth-round victory in two hours against her 22-year-old opponent.
It was an admirable effort by Stephens, however, who fell just short of completing the 'double' over the Williams family, having knocked out sister Venus in the opening round.
Stephens, who was hammered by Williams on clay in Madrid last month, had never progressed beyond the fourth round at Roland Garros before but must have felt her luck was changing when she secured the opening set in just 23 minutes.
The world number 40 outshone her illustrious opponent who, at times, seemed to be running on empty as shot after shot raced past her on the way to being broken three times.
Williams was not helped by 15 unforced errors but there were signs of improvement in the second set as the first six games went with serve.
Stephens then fought off four break points in game seven as Williams finally found something in the tank, but a fifth fell in favour of the world number one as she edged ahead for the first time in the match.
The contest was back on serve in the next game as Stephens broke, but Williams put her foot down once more in the 11th to secure another break before serving it out to usher in a decider.
It was the first set Stephens had conceded in this year's tournament while Williams moved into her third successive three-setter - and perhaps still feeling the effects of the last round against Victoria Azarenka in her limbs.
However, experience began to tell as the 19-time grand slam winner saved a break point with a forehand winner in game two and then got the break she needed three games later when Stephens pushed a weak forehand into the net.
Stephens continued to force her opponent around the court but her confidence seemed to have dropped and Williams wrapped up the win with another break when her opponent fired a backhand into the net.
Williams will now face 17th-seeded Italian Sara Errani in the quarter-finals.
There was another upset in the last match on Monday as fourth seed Petra Kvitova was knocked out by Timea Bacsinszky.
Bacsinszky has never been further than the third round at a grand slam before, but the world number 24 came from a set down to beat Kvitova 2-6 6-0 6-3.
The Swiss will now play Belgium's Alison van Uytvanck in the quarter-finals while Williams will face Italian Sara Errani.
Serbian Ana Ivanovic and Ukraine's Elina Svitolina complete the last eight.
