Serena Williams survived another French Open scare as the top seed was tested to the full by American compatriot Sloane Stephens on court Philippe Chatrier.
With second seed Maria Sharapova tumbling out of the tournament earlier on Monday, 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.