MELBOURNE (AFP) -  A laser-focused Ashleigh Barty dismantled American giant-killer Amanda Anisimova on Sunday (Jan 23) to battle into an Australian Open quarter-final against Jessica Pegula.

The steely-eyed Australian world No. 1 won 6-4, 6-3 on Rod Laver Arena to halt the charge of the unseeded American who stunned defending champion Naomi Osaka in round three.

Top-seed Barty, who is aiming to become Australia’s first women’s champion in 44 years, will now face 21st-seeded American Pegula following her upset of Greek fifth seed Maria Sakkari 7-6 (7-0), 6-3 to make her second straight quarter-final in Melbourne.

“She’s an incredible athlete, she’s an incredible competitor. One of her best attributes is she is able to turn up point after point,” said Barty of Anisimova.

“She’s got an exceptional game that puts you under the pump right from the get-go and it was nice to hold firm tonight and bring the points back into my patterns more regularly and the big ones when it mattered most.”

It was a rematch of the pair’s memorable 2019 French Open semi-final.

Barty was staring down the barrel of defeat then after a first-set collapse, but fought back to win the match and eventually the title.

It proved to be a turning point in her career and she has now been world No. 1 for 112 consecutive weeks.

Earlier, French Open champion Barbora Krejcikova blew away former two-time Melbourne champion Victoria Azarenka, who had a neck problem, to set up a last-eight clash with unseeded American Madison Keys.

Fourth seed Krejcikova of the Czech Republic powered through 6-2, 6-2 against the Belarusian, who won the title in 2012 and 2013.

"It was really amazing today because she is a champion here and she likes this court, she's very experienced on this court," said Krejcikova of Azarenka.

Keys raced past Spain's Paula Badosa, seeded eight, 6-3, 6-1.

"Absolutely amazing," said Keys. "I served pretty well and I think I returned pretty well."