Wimbledon champion Marketa Vondrousova has suffered an injury scare less than a fortnight before her title defence is due to start.

The Czech slipped and fell when leading 5-3 in the first set of her second-round match against Anna Kalinskaya at the Berlin Open.

Vondrousova clutched her right hip and called for a medical time-out before retiring two games later, with the score at 5-5.

Wimbledon takes place from 1-14 July, with Vondrousova set to start her title defence on the second day

The 24-year-old became the first unseeded player to win the Wimbledon women's singles title when she beat Ons Jabeur in the final.

Russia's Kalinskaya will face world number three Aryna Sabalenka, who brushed aside Daria Kasatkina 6-1 6-4.

Eight of the world's top 10 are competing in Berlin, with only top-ranked Iga Swiatek and world number seven Jasmine Paolini absent.

Jabeur fought back from a set down against Linda Noskova to set up a quarter-final match against Coco Gauff.

World number two Gauff beat Russia's Ekaterina Alexandrova 7-6 (8-6) 6-2.

Third seed Elena Rybakina claimed a 6-4 7-5 victory over Veronika Kudermetova to set up a last-eight encounter with former world number one Victoria Azarenka.

At the Birmingham Classic, Britain's Harriet Dart fell to a 6-3 6-4 defeat by Czech second seed Barbora Krejcikova.

Meanwhile, British number one Katie Boulter is guaranteed to secure a Wimbledon seeding after Elise Mertens, who sits one place behind Boulter in the rankings, retired injured against Caroline Dolehide.