No. 1 Barty upset in Australian quarterfinals by Muchova

6-2 victory in the Australian Open quarter-final.

World No. 1 Ashleigh Barty's quest to become the first Australian to win their home Grand Slam since Chris O'Neil in 1978 is over after she was beaten in the quarterfinals by 25th seed Czech Karolina Muchova on Wednesday.

The Australian golden girl was in full control early on against Czech world number 25 Karolína to win the first set 6-1 in just 24 minutes before choking to lose the next two sets on Rod Laver Area.

Muchová will now take on either USA young gun Jessica Pegula or Jennifer Brady who will face off later on Wednesday.

She left the court at the first changeover of the second set for a medical time out and confirmed after the match that she didn't receive treatment for the abdominal injury which saw her pull out of the Gippsland Trophy a fortnight ago.

"I tried to get back, played a bit faster rally so we don't play that long ones [like] in the first set and it worked well".

Barty, the 2019 French Open champion, had made a flying start to her year, winning the warm-up Yarra Valley Classic and had not lost a set before meeting Muchova.

She broke again for a 5-0 lead and sealed the set in 24 minutes, with Muchova winning only 11 points, hitting just one victor against 13 unforced errors.

"My head was spinning and I was a bit lost so I took a break", she said in her on-court interview.

"So they cooled me down a bit with ice and it helped me".

After coughing up her first double-fault in her next service game, Barty had to fight off another two break points to level the set at 3-3 with Muchova's time-out clearly halting the Australian's momentum.

Comebacks have been a staple in the tournament for Muchova, who rallied in earlier matches to win sets after trailing 5-0 and 4-0. After nine games, Muchova had one victor and 18 unforced errors.

The Czech was far more competitive and earned another break for 5-3 then took the set as a lost-looking Barty's error count mounted.