Karolina Muchova proved to be more than enough for off-the-boil fourth seed Maria Sakkari as the comeback Czech knocked out the Roland Garros fourth seed 7-6(5), 7-6(4) on Wednesday.
The 81st ranked winner missed seven months with an abdominal injury and was absent from the end of the US Open to the Miami event in late March.
But the one-time Top 20 contender made her Greek opponent the fifth Top 10 seed to lose here in barely three and a half days of play.
Muchova had to struggle to get the job done, requiring eight set points to capture the first set, with Sakkari threatening as she fought from 5-2 down.
The second set was equally challenging, with the winner ending it in two and a half hours as she forced Sakkari to save 13 of 16 break chances.
Muchova now plays Amanda Anisimova after the one-time Paris semi-finalist beat Croat Donna Vekic 6-4, 6-1.