Laura Siegemund has reached the quarter-finals of the WTA tournament in Stuttgart for the first time since winning the title in 2017.

The 34-year-old Swabian was leading 6-4, 3-1 in the last 16 on Thursday when Greek world number five Maria Sakkari retired. This is the third time Siegemund has reached the round of the best eight at her home tournament.

On Friday she will play Liudmila Samsonova. The unseeded Russian surprisingly advanced against the Czech top player Karolina Pliskova.

Siegemund had started the tournament, which is endowed with 611,210 euros, with lower expectations because she lacked match practice after a knee operation. She had received a wild card to take part in the top-class event, but due to her break she fell out of the top 200 in the world rankings.

German number one Angelique Kerber suffered another disappointment with her first-round exit on Wednesday.