Former finalist Sloane Stephens was thrashed by Barbora Krejcikova in the fourth round of the French Open.
World number 33 Krejcikova, who beat Elina Svitolina in the third round, is now on a nine-match unbeaten streak.
She will play either American teenager Coco Gauff or Ons Jabeur of Tunisia in the quarter-finals.
Krejcikova, a three-time Grand Slam doubles champion, made her singles breakthrough at last year's French Open when she reached the fourth round.
She won the Strasbourg Open in the lead up to this tournament and was dominant against world number 59 Stephens, saving all three break points she faced.