Melbourne: Coco Gauff may have gone from the hunter to the hunted but didn’t fall prey to a courageous Marta Kostyuk to book a spot in the Australian Open semi-finals for a first time. The fourth seed and reigning US Open champion extended her grand slam winning streak to a dozen matches with a rollercoaster 7-6 (8-6) 6-7 (3-7) 6-2 victory in Tuesday’s first women’s quarter-final at Melbourne Park. She had to scrap for more than three hours in scorching heat as 21-year-old Kostyuk overcame painful blisters to threaten a huge boilover. The Ukrainian underdog eventually yielded as Gauff progressed to a semi-final on Thursday against second-seeded defending champion Aryna Sabalenka, who outclassed Czech world No.11 Barbora Krejcikova 6-2 6-3. The American conceded to serving up a sub-par performance but was satisfied in borrowing a page out of her coach Brad Gilbert’s book to win ugly. “Today was definitely a C game,” said the 19-year-old after becoming the first teenage woman since Maria Sharapova to win 12 consecutive grand slam matches this century. “I didn’t play my best tennis but really proud that I was able to get through today’s match. Hopefully I got the bad match out of the way and I can play even better.” The pair racked up 107 unforced errors between them across 246 points, compared to 56 winners in gruelling conditions on RLA. Kostyuk’s initial barrage caught Gauff off guard before the 19-year-old recovered from 1-5 down to claim the first set. “I knew going in, playing her, it was (going to be) a tough match,” said Gauff. “She’s pretty athletic, and we kind of play similar. Today she was just more offensive, which I wish I was taking the offense from the beginning.” Last September, Gauff became the first teenager since 23-time grand slam champion Serena Williams in 1999 to win the US Open title. Playing her final major as a teen, the Florida native said she’d noticed a change in her opponents’ demeanour after bagging her first slam. “There is definitely a change in just the energy,” Gauff said when asked about going from hunter to hunted. “You do feel like you’re the one to beat and I feel like people step on court and they … play their best games because there’s no pressure. “I definitely feel a little change. But also, at the same time, not really, because when I was young nobody wanted to lose to a 15-year-old, so I felt people played really hard too. “There’s a quote, ‘it’s … easier to get to the top but harder to stay there’. The goal is to stay here as long as possible and keep going upwards.” Gauff has won both her previous slam semi-finals, easily accounting for Italian Martina Trevisan at the 2022 French Open and Czech Karolina Muchova at Flushing Meadows last year. She was unaware of her flawless last-four record at the majors so far but wasn’t shying away from it. “It does give me confidence knowing that at least in that stage of a grand slam that my nerves are usually settled,” said Gauff. “Hopefully I can go out there and be settled.”