Australia's Ashleigh Barty reacts during her quarterfinal match against Karolina Muchova of the Czech Republic at the Australian Open tennis championship in Melbourne, Australia, Feb 17, 2021. (WILLIAM WEST / AFP)

MELBOURNE - World number one Ashleigh Barty’s dream of become the first homegrown Australian Open champion since 1978 was shattered on Wednesday after an extraordinary 1-6 6-3 6-2 quarter-final loss to Czech Republic's Karolina Muchova.

The Czech was a player transformed after taking a medical timeout when she started feeling dizzy in the Melbourne heat and rallied to secure a place in her first Grand Slam semi-final.

The 24-year-old will meet American Jennifer Brady for a place in the final against Serena Williams or Naomi Osaka.

“It’s heartbreaking, of course,” said world number one Ashleigh Barty, who was hoping to become the first homegrown Australian Open champion since Chris O’Neil in 1978

“It’s heartbreaking, of course,” said Barty, who was hoping to become the first homegrown Australian Open champion since Chris O’Neil in 1978.

“But will it deter me? Will it ruin the fact we’ve had a really successful start to our season? Absolutely not. The sun will come up tomorrow.

“We go about our work again. You’re either winning or your learning. We won’t let ... this particular hour of tennis deter us from what we’re trying to do.”

ALSO READ: Barty returns to action after 11 months for Aussie Open warmup

Barty had started the contest like a woman possessed and conceded only six points in racing to a 5-0 lead in just over a quarter of an hour, wrapping up the first set soon afterwards.

Karolina Muchova of the Czech Republic (center) receives medical treatment during her quarterfinal against Australia's Ash Barty at the Australian Open tennis championship in Melbourne, Australia, Feb 17, 2021. (ANDY BROWNBILL / AP)

Muchova had some treatment at her chair early in the second set and then took the lengthy medical timeout, leaving the former French Open champion trying to stay loose by doing stretches on court.

Although not as dominant as the Australian had been in the opening set, the Czech quickly levelled up the match at 1-1 to become the first player to take a set off the top seed at this tournament.

Barty continued to carve out chances on Muchova’s serve but failed to convert them and her error count soared as she tried to finish points too early to wrest back the momentum.

Muchova, the 25th seed, hit 17 winners over the match and settled her nerves sufficiently to serve out for the win at the first time of asking, sealing her place in the last four with an ace.

ALSO READ: Australian Open: Williams to face Osaka in semifinals; Dimitrov exits

Jennifer Brady of the United States hits a forehand return to compatriot Jessica Pegula during their quarterfinal match at the Australian Open tennis championship in Melbourne, Australia, Feb 17, 2021. (HAMISH BLAIR / AP)

Brady battles through

In a separate match, Jennifer Brady battled through her frustrations to overhaul friend and United States teammate Jessica Pegula 4-6 6-2 6-1 and reach her maiden Australian Open semi-final.

The 22nd seed Brady has a golden chance to reach her first Grand Slam final after world number one Barty was shocked by Muchova in the early quarterfinal.

With Serena Williams to face Naomi Osaka in the other semi-final, the Australian Open could have another all-American title match on Saturday, four years after Serena beat her sister Venus for the 2017 championship.

Brady’s effort is more remarkable for having been one of the 72 players in hard quarantine before the tournament, unable to train on courts for five hours a day like the rest of the field.

READ MORE: 'Players don't want season to continue with quarantines'

Despite the limited preparation, and a raft of taxing rallies against Pegula, there was no sign of her flagging in the heat.

Russia's Daniil Medvedev receives an interview after his win over compatriot Andrey Rublev in their quarterfinal match at the Australian Open tennis championship in Melbourne, Australia, Feb 17, 2021. (ANDY BROWNBILL / AP)

Medvedev extends winning streak

Over at the men’s side, Russian Daniil Medvedev secured a spot in the Australian Open semi-finals with a 7-5 6-3 6-2 victory over friend and compatriot Andrey Rublev, extending his winning streak to 19 matches.

It was Rublev’s fourth straight defeat to Medvedev, who has not lost a match since October. Fourth seed Medvedev had won all his previous matches against Rublev in straight sets.

“We had some unbelievable rallies, I’m one of the first players to make Andrey so tired... It’s hard to play (a friend) but we’re all so competitive, just need to win, get to that Grand Slam semi-final," Medvedev said in an on-court interview, after receiving a massage on his left thigh following the win.

Fourth seed Daniil Medvedev of Russia has not lost a match since October

“That was one of my best matches ... I beat him in three sets not even with a tiebreak so I’m really happy,” 

ATP Finals winner Medvedev raised his game during the important points and sealed the contest with a forehand winner to set up a last-four meeting against either second-seeded Spaniard Rafa Nadal or fifth seed Stefanos Tsitsipas of Greece.

READ MORE: Djokovic edges out Zverev to reach semi-final

Russian qualifier Aslan Karatsev will meet world number one Novak Djokovic in the other semi-final on Thursday, with the prospect of an all-Russian men’s final looming on Sunday.

The Australian Open will be able to open its gates to fans for the last four days of the tournament after the state of Victoria announced that a snap coronavirus lockdown would be lifted at midnight on Wednesday.