U.S. Open champion Coco Gauff is into the semifinals of the Australian Open after beating Marta Kostyuk 7-6 (6), 6-7 (3), 6-2 in an error-strewn match at Melbourne Park. The American saved two set points as she came from 5-1 down to win the opener but needed a deciding set to claim victory after three hours, eight minutes. She will play either defending champion Aryna Sabalenka or Barbora Krejcikova in the semifinals on Thursday. Men’s No. 1 Novak Djokovic is in action later, taking on Taylor Fritz for a place in the semifinals.