World No 1 Aryna Sabalenka complained after her second-round Berlin Open match against Switzerland's Rebeka Masarova was suspended due to bad light and dew on Wednesday.
Sabalenka won the first set 6-2 before the umpire suspended play until Thursday.
The Belarusian was upset and told the umpire: "You are stopping the match because she says that side is slippery? I just played two games on that side."
Sabalenka claims the set 💫
— wta (@WTA) June 18, 2025
Due to court conditions the match will conclude tomorrow!#BTO pic.twitter.com/ZqcAW9Ni89
The previous match, won by Liudmila Samsonova against third seed Jessica Pegula, took three hours and 21 minutes to complete.
Samsonova beat the American 6-7 (8/10), 7-5, 7-6 (7/5) in a match including two tie-breaks.
Fighting spirit 🥊@LiudaSamsonova takes out the defending champ to secure her spot in the quarterfinals in Berlin!#BTO pic.twitter.com/vlO2K9rVXS
— wta (@WTA) June 18, 2025
The incident comes just days after Sabalenka lost the French Open final to Coco Gauff, then made comments for which she later apologised.
The 27-year-old said the French Open final was "the worst final I've ever played", adding: "I don't think she won the match because she played incredibly well, but because I made all those mistakes."
Before the Berlin tournament, Sabalenka told Eurosport her comments were "simply completely unprofessional".
"I let my emotions guide me. I absolutely regret what I said."
Sabalenka has never won a WTA title on grass or reached a Wimbledon final.
Earlier on Wednesday, two-time Wimbledon runner-up Ons Jabeur beat Jasmine Paolini 6-1, 6-3 to reach the last eight.
The victory was the Tunisian's first over a top-five opponent since her run to the final at Wimbledon in 2023.
Jabeur, who won on the Berlin grass in 2022, will be joined in the quarters by eighth seed Paula Badosa, who beat Emma Navarro 7-6 (7/2), 6-3.
One of the oldest women's tournaments in the world, the Berlin Open switched from clay to grass courts in 2021 and has since become a popular warm-up event for Wimbledon, which starts at the end of the month.