Iga Swiatek to face Aryna Sabalenka again in Stuttgart final after Ons Jabeur retires
The Pole on Sunday will face Aryna Sabalenka (24) in a repeat of last year's final, following the Belarusian's comfortable straight sets victory over Anastasia Potapova (22).
Tunisian Jabeur, on a seven-match winning run after recovering from injury and surgery earlier this year, looked to have hurt herself during the last point of the first game.
The world number four, fresh from her title win in Charleston earlier in the month, took a medical timeout but despite playing on with her left calf bandaged for two more games she decided to stop with Swiatek 3-0 up.
"I really tried but at that point I don't know what happened," a tearful Jabeur said. "I was excited to play Iga and seeing that the stadium is full. I am sorry about it."
Australian Open winner Sabalenka needed just 58 minutes to storm into her third straight Stuttgart final with a 6-1 6-2 demolition of Potapova.
Sabalenka, who last year lost to Swiatek, raced to a 4-0 lead, breaking her opponent twice.
World number 24 Potapova was playing catch-up throughout and was very vulnerable on her weak second serve.
She was equally helpless in the second set with Sabalenka breaking early again as she won the first eight points.
The world number two then raced back from 30-0 down with a string of big serves at 5-2 to finish off the game and reach her fourth final of the year.