Anna Kalinskaya defeated former world number one Victoria Azarenka 6-1, 6-7 (3-7), 6-1 on Saturday to reach the Berlin grass court tournament final, but her opponent is not yet known as weather affected the event again.
The other semi-final between top seeded US Open champion Coco Gauff and fellow American Jessica Pegula was suspended for the night due to rain, with Pegula leading 7-5, 6-6 (3-1).
The scoreline means that Pegula is four points away from the final to be played later Sunday.
Australian Open quarter-finalist Kalinskaya meanwhile beat Azarenka in 2 hours 10 minutes to reach her second final of the year, the other being in Dabai where she lost against Jasmine Paolini.
Kalinskaya rallied from 4-1 down in the second set but was eventually uable to win in straight sets.
Earlier Saturday, she and Gauff had to play their rain-delayed quarter-finals but neither had to play full matches as their opponents Ons Jabeur and Aryna Sabalenka retired.
With Azarenka also winning her quarter-final prematurely the previous day when former Wimbledon champion Elena Rybakina retired with illness, the only completed last eight match at the event was Pegula's 7-6 (7-2), 3-6, 6-3 over Katerina Siniakova.
Gauff saved two set points and needed 11 herself to win the first set against Jabeur 7-6 (11-9). The Tunisian then retired ill after being assessed by the trainer.
Kalinskaya was 5-1 up when Australian Open champion Sabalenka retired with what appeared to be shoulder and neck problems.
"I was happy with how I was able to play," Gauff said. "Of course, I send my best wishes to Ons. It's not the way you want to finish a match, especially with someone who is so nice on and off the court."
The busy schedule came because of rain the previous day when Azarenka advanced while Pegula led 4-2 in the first set en route to her first career semi-final on grass.
Another injury casualty at the tournament was Marketa Vondrousova who retired mid-match just over a week before the start of her Wimbledon title defence.