Top seed Elina Svitolina was toppled in straight sets by Maria Sakkari at the WTA’s Ostrava Open.
Sakkari, from Greece, broke the serve of world No.5 Svitolina five times and blasted 32 winners on her way to a 6-3 6-3 victory and a place in the quarter-finals.
Victoria Azarenka continued her fine form on hard courts by coming from a set down to beat home hope Barbora Krejcikova 2-6 6-2 6-1.
Belarusian fourth seed Azarenka has now won 12 of her past 13 matches on the surface, winning the Western & Southern Open before reaching her fifth grand slam final at the US Open.
Former French Open champion Jelena Ostapenko shocked fifth seed Petra Martic 6-3 6-1 in less than an hour while seventh seeded Elise Mertens beat Amanda Anisimova 6-2 6-3.