Ash Barty has passed her sternest test yet to move safely into the Australian Open quarterfinals at Melbourne Park.
The world No. 1 dropped serve for the first time all tournament before seeing off US prodigy Amanda Anisimova 6-4, 6-3 in one hour and 14 minutes on Sunday night.
The 25-year-old Wimbledon champion is the first home hope to reach at least the last eight of the Open for four consecutive years since Wendy Turnbull in 1984.
Unbeaten in nine matches since hiring Aussie coaching guru Darren Cahill on a summer trial basis, and having taken out defending champion Naomi Osaka in the third round, Anisimova shaped as a huge threat to the top seed.
In the pair's only previous meeting, Barty had to pull out all stops in an epic comeback from a set and 3-0 down in the 2019 French Open semifinals.
While Barty backed up that steely victory to capture her maiden Grand Slam title two days later in Paris, then climb to world No. 1, Anisimova's own seemingly inevitable rise to super-stardom stalled two months after that Roland Garros run with the sudden death of her father.
But with Cahill in her corner, Anisimova has burst back to life this summer, winning her second career title in Melbourne and then powering into the last 16 of a major for only the second time.
Even after dropping the opening set against Barty on Sunday, the big-hitting 20-year-old continued to take the fight to title favourite.
She broke the world No. 1 in the second game of the second set, snapping Barty's incredible streak of 63 consecutive service games held, to briefly silence the Rod Laver Arena crowd.
Barty, though, kept her cool, breaking straight back, then twice more to clinch a ninth successive win of her still-undefeated 2022 season.
"It was nice to be able to hold firm tonight and bring the points back into my patterns more regularly and the big ones when it mattered most," Barty said.
"Amanda's an incredible athlete. She's an incredible competitor. One of the best attributes is that she's able to turn up point after point after point,.
"I enjoyed testing myself against her. She's got an exceptional game that puts you under the pump right from the get go.
"It's just nice to see her back playing her best tennis. She's a champion. She's going to be in deep stages of a lot of majors in her future, that's for sure."
Hoping to break the host country's 44-year Open singles title drought, Barty will play another American, 21st seed Jessica Pegula, on Tuesday for a place in the last four at Melbourne Park.