Germany's Carina Witthoeft knocked out the highest seed left in the Luxembourg Open after sweeping aside Kiki Bertens 6-1 6-2.
Bertens was the tournament's second seed but managed to get just 38 per cent of her first serves in play as she was beaten in just 57 minutes.
None of a strong British contingent made it beyond the last eight after Heather Watson and Naomi Broady were dispatched by Elise Mertens and Monica Puig respectively.
Fifth seed Mertens is now the highest ranked player left in the draw and the semi-final line-up is completed by Pauline Parmentier, who crushed Johanna Larsson 6-1 6-2.
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