After beating defending champion Simona Halep in the second round, Ana Ivanovic was subject of an upset herself at the Dubai Tennis Championships on Thursday.
The world number 17 looked set to reach successive semi-finals following her victory over Halep, but Barbora Strycova had other ideas.
Ivanovic started well with a service game to love but she struggled to find her rhythm as Strycova took control with her powerful groundstrokes.
Strycova's all-action style ensured Ivanovic - who made 32 unforced errors - was given no chance of dominating rallies, but after they had traded breaks in the first set they needed a tie-breaker to separate them.
Having opened up a 5-3 lead Ivanovic crumbled under the pressure as Strycova won five in a row to move ahead, momentum she maintained in the second set as she completed a 7-6 (7-5) 6-3 victory.
The Czech will meet Caroline Garcia in the last four after she booked a first WTA Premier semi-final with a comfortable 6-3 6-4 win over Andrea Petkovic.
The other last-four clash sees Sara Errani face Elina Svitloina after their respective three-set wins over Madison Brengle and Coco Vandeweghe.