Aryna Sabalenka fought back to defeat Czech 20-year-old Nikola Bartunkova in the Berlin Open quarter-finals on Friday.
The world number one prevailed 2-6, 7-6 (7-2), 6-4 in hot conditions at the Wimbledon grass warm-up.
“I think a miracle thing happened,” said Sabalenka, without a tournament win since March.
“I just saw this little doubt in her head and I tried to really use this small opportunity that I had and I’m glad I somehow found my rhythm.”
She next faces third seed Jessica Pegula, who beat US compatriot Madison Keys 7-6 (7-5) 7-6 (8-6).
Linda Nosková also won through and will meet the Philippines' Alexandra Eala, who stunned Ukrainian sixth seed Elina Svitolina 6-3, 6-4.
