Defending champion Garbine Muguruza, 2021 finalist Barbora Krejcikova and top seed Aryna Sabalenka were all eliminated from the Dubai Tennis Championships on Wednesday.
A day of upsets left Ons Jabeur, the eighth seed, as the top remaining player in the draw.
Some big names helped deliver the shocks, though, with world number two Sabalenka usurped by two-time Wimbledon champion and 2013 Dubai winner Petra Kvitova in straight sets.
Muguruza did not look like being one of the scalps as her title defence continued against Veronika Kudermetova.
But after taking the first set, the reigning WTA Tour Finals champion went down 3-6 6-4 6-4.
French Open champion Krejcikova, beaten by Muguruza in the final last year, also exited the tournament at the hands of Dayana Yastremska 6-3 7-6 (7-3).
Dubai QFs after a day of early upsets, which saw the exits of top seeds Sabalenka, Krejcikova and defending champion Muguruza:
Kvitova vs. Ostapenko (4-3)
Halep vs. [8] Jabeur (1-1)
[LL] Teichmann vs. Kudermetova (0-2)
[Q] Vondrousova vs. [Q] Yastremska (1-1)
Iga Swiatek let a set lead slip to Jelena Ostapenko, while two-time Dubai champion Elina Svitolina collapsed to lucky loser Jil Teichmann 7-6 (7-0) 6-2.
Jabeur, a winner against Jessica Pegula, was the only seed to win in a ruthless round of 16.
However, her reward in a still stacked quarter-final draw is a meeting with Simona Halep, another who has twice won in Dubai.