World number five Anett Kontaveit slipped out of the Indian Wells Open after a 3-6 7-5 7-6 (7-5) loss to Marketa Vondrousova.
Kontaveit was the second-highest seed remaining in the tournament entering Monday’s play, and appeared to be on her way through to the fourth round after breaking twice in the opening set.
Yet Vondrousova got the better of her Polish opponent in a topsy turvy second set, forcing a decider that starter in frantic fashion, with a concession of serve in each of the opening five games.
Vondrousova held to end that street yet was pulled back to 4-4 by a resurgent Kontaveit, though the Czech world number 33 eventually closed the match out at the fourth time of asking in the tie-break to tee up a clash with Veronika Kudermetova.
Kudermetova should be fresher for the last-16 tie after her match ended when an injury forced Marie Bouzkova to retire.
Russian Kudermetova, who is playing under a neutral banner at the tournament, held a 6-4 lead from the first set but had been broken to love in the game immediately preceding Bouzkova’s retirement.
Sixth seed Maria Sakkari turned in a stunning performance to down two-time Wimbledon champion Petra Kvitova, wiping the Czech off the floor 6-3 6-0.
Sakkari needed to save two break points to serve the first set out, before icing the match with a near-flawless bagel.
The draw is kind to Sakkari in the fourth round though she will have to be wary of world number 409 Daria Saville after the Australian upset Elise Mertens 6-3 4-6 6-3.
It is the second consecutive top-25 opponent Saville has beaten this tournament after surprising world number 10 Ons Jabeur in the previous round.
US Open runner-up Leylah Fernandez, meanwhile, saw off Shelby Rogers 6-1 3-6 6-3 to tee up a tie with fifth seed Paula Badosa.