Wimbledon champion Garbine Muguruza was one of three players forced to retire in the last 16 of the Stuttgart Open.

The Spanish second seed pulled out with a back problem after losing the first set 7-5 against Russian Anastasia Pavlyuchenkova.

Germany’s Angelique Kerber withdrew with a leg injury after going 6-0 2-0 down against Estonia’s Anett Kontaveit.

Czech Marketa Vondrousova won the first set against Ukraine’s Elina Svitolina but also quit with a leg problem.

Third seed Svitolina, who recovered to lead 2-6 6-1 3-2 before Vondrousova’s retirement, will now play French sixth seed Caroline Garcia, who overcame Marta Kostyuk of Ukraine 6-1 3-6 7-5.

Kontaveit and Pavlyuchenkova now face each other in the quarter-finals, while American Coco Vandeweghe booked a meeting with top seed Simona Halep after winning 6-4 4-6 6-3 against defending champion Laura Siegemund of Germany.

Czech fifth seed Karolina Pliskova beat Russia’s Veronika Kudermetova 7-6 (7-4) 6-3 and will now meet fourth seed Jelena Ostapenko after the Latvian won 6-3 6-0 against Zarina Diyas of Kazakhstan.

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