Coco Gauff dropped a set for the second match in a row before clawing her way into a third consecutive Australian Open quarter-final on Sunday as she zeroes in on a maiden Melbourne title.
The American third seed rolled over seasoned Czech 19th seed Karolina Muchova 6-1, 3-6, 6-3 on Margaret Court Arena, but needed nearly two hours to do so.
She will play either Ukraine's 12th seed Elina Svitolina or 18-year-old Russian eighth seed Mirra Andreeva for a place in the semi-finals.
"She definitely elevated her game and I thought sometimes I was a bit passive, but it's really tough to play her," said the 2025 French Open and 2023 US Open champion.
"She plays with so much variety, you never know what you're going to do. I'm really happy to get through this one today."
The 21-year-old Gauff has never gone beyond the last four at Melbourne Park.
Muchova had pedigree, bidding to make an eighth career Grand Slam quarter-final and she made life difficult after a slow start.
Gauff had a psychological advantage before a ball was hit, winning all four previous encounters and never losing a set, including an easy victory at the United Cup this month.
And she made the best possible start, with back-to-back breaks of Muchova who blasted a slew of unforced errors, racing 4-0 in front.
Gauff's serve has been her Achilles' heel in recent times, but she had few issues with it initially.
Instead, it was Muchova who struggled, winning just %33 her first-serve points in the set.
The Czech player finally held for 1-5 to avoid a dreaded bagel, but it just delayed the inevitable with Gauff taking the set in 30 minutes.
Muchova began with more intent in set two, holding then taking advantage as Gauff's serving yips returned to ease 2-0 ahead.
Gauff broke back but again failed to hold and Muchova took a set off her for the first time in her career.
The crucial moment in the third set came when Muchova spilled a forehand long on serve to give Gauff three break points in game three, with another loose shot from the Czech sealing her fate.
Gauff held serve for 4-1 and safely sealed the win on her fourth match point.
