The American fourth seed wore down the Ukrainian in hot conditions to clinch a scrappy encounter 7-6 (8/6), 6-7 (3/7), 6-2 in three hours and eight minutes.
US Open champion Coco Gauff overcame huge resistance from the unseeded Marta Kostyuk Tuesday to move into her first Australian Open semi-final.
The American fourth seed wore down the Ukrainian in hot conditions on Rod Laver Arena to clinch a scrappy encounter 7-6 (8/6), 6-7 (3/7), 6-2 in three hours and eight minutes.
She will face either defending champion and second seed Aryna Sabalenka or ninth-seeded Barbora Krejcikova on Thursday for a place in the final.
After showing ominous form to race into the last eight, it was a far from convincing display by the 19-year-old, who struggled on serve and fluffed countless opportunities.
“Happy, really proud of the fight I showed today,” said Gauff, who had never progressed beyond the fourth round at Melbourne Park in four previous attempts.
“Marta is a tough opponent… I really fought and left it all on the court today.”(HT)