Defending Australian Open champion Aryna Sabalenka has continued her charge towards back-to-back titles after demolishing ninth seed Barbora Krejcikova in a one-sided quarter-final.

In a match that started more than two hours late because of farcical scheduling, the world No.2 put on another clinic on Rod Laver Arena to win 6-2 6-3 in 71 minutes.

Sabalenka has looked closed to invincible in this tournament, dropping just 16 games and winning every set across her first five matches.

The 25-year-old did drop a service game late in the second set to prove she was human, but still cruised to a 12th straight victory at Melbourne Park.

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“It was a really great match and I played really great tennis and I hope I can just keep playing that way or even better,” Sabalenka said.

“I’ve been working so hard last year and this pre-season, I think it’s all about hard work on the practice court so you’re ready for the matches.”

Krejcikova entered the match having been on court for four hours longer than Sabalenka.

The Belarusian is aiming to become the first woman since countrywoman Victoria Azarenka in 2012 and 2013 to win two-straight Australian Open titles.

Sabalenka will meet US Open champion Coco Gauff in a mouth-watering semi-final after the American fourth seed survived a three-hour epic against Ukraine’s Martya Kostyuk.

Whoever wins that encounter will start as a heavy favourite in the final, with a rank outsider certain to be in the decider.

The quarter-finals on Wednesday involve unseeded Czech teenager Linda Noskova and Ukraine qualifier Dayana Yastremska, and Russian Anna Kalinskaya against China’s Qinwen Zheng.

Sabalenka was unable to add to her sole grand slam title after last year’s Australian Open despite reaching at least the semi-finals in the the three other majors.

-AAP