Marta Kostyuk of Ukraine stormed back in the first set and won a tense tiebreaker, and then cruised to a semifinal victory over top-seeded Jessica Pegula of the U.S. at the Cymbiotika San Diego Open on Saturday night.

With the 7-6 (4), 6-1 victory, Kostyuk, the sixth seed, will take on Katie Boulter of Great Britain in Sunday's final. Boulter, ranked 49th in the world, crushed the third seed, Emma Navarro of the U.S., 6-3, 6-1.