Serena Williams of the United States (left) is congratulated Aryna Sabalenka of Belarus (right) after winning their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Feb 14, 2021. (HAMIS BLAIR / AP)

MELBOURNE - Naomi Osaka and Serena Williams advanced into the quarterfinals of the Australian Open on Sunday, while Dominic Thiem slumped out of the tournament in lackluster fashion.

Fans remained absent from Melbourne Park for a second day because of the state of Victoria’s coronavirus lockdown

Williams, who is chasing a record-equaling 24th Grand Slam title, stormed into the next round with a gritty 6-4 2-6 6-4 victory over Belarusian Aryna Sabalenka.

The match was a big test for Serena Williams, who was up against one of the few players on the women’s tour capable of matching her power from behind the baseline

The match was a big test for Williams, who was up against one of the few players on the women’s tour capable of matching her power from behind the baseline.

ALSO READ: Tough road ahead for Serena's pursuit of 24th Grand Slam title

“I’m happy to get through that one,” Williams said in an on-court interview. “It wasn’t easy and I knew it wasn’t going to be easy. She was teeing off on every shot.

“Even the games that I lost were super close, one shot here and one shot there, and I just felt like, ‘Serena you’ve got this, you’ve just got to keep going.’”

The players went toe-to-toe in an even first set until Williams pounced late to break Sabalenka for the first time and take a 1-0 lead.

The roles were reversed at the start of the second, however, with Sabalenka breaking Williams in her first two service games.

Serena Williams of the United States falls during her fourth round match against Aryna Sabalenka of Belarus (not in frame) at the Australian Open tennis championship in Melbourne, Australia, Feb 14, 2021. (HAMIS BLAIR / AP)

The American clawed a break back but was powerless in the face of Sabalenka’s onslaught as the seventh seed broke once more for a 4-1 lead before sending the match into a decider.

With the pressure ramped up in the third it was Sabalenka who blinked first, making several errors on serve to hand Williams a 3-1 lead.

The Belarusian broke back and then levelled the set at 4-4 with a hold to love but the pressure finally told with Sabalenka serving to stay in the match trailing 5-4.

Sabalenka double-faulted to give Williams a 15-30 lead and netted a forehand to hand her two match points, conceding the match by sending a forehand long.

Japan's Naomi Osaka hits a forehand return to Spain's Garbine Muguruza (not in frame) during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Feb 14, 2021. (HAMISH BLAIR / AP)

Osaka battles back from the brink

In an earlier match, Osaka saved two match points as she battled back from the brink to reach the quarterfinals with a 4-6 6-4 7-5 victory over in-form Garbine Muguruza.

The Japanese third seed was chasing the match from the start on Rod Laver Arena and looked defeat square in the face in the third set when the Spanish 14th seed had two opportunities to win the match with a break of serve.

Next up for Naomi Osaka is an all-Asian quarter-final against Hsieh Su-wei of Chinese Taipei, who will be playing in the last eight of a Grand Slam for the first time

Osaka saved both match points - the first with an ace to turn the tide in the contest decisively and Muguruza exited the tournament a couple of games later after failing to win a point in her final service.

ALSO READ: Australian Open kicks off with big name exits

“I’m tired right now, that was tough,” said Osaka, who mixed 40 winners with 36 unforced errors over the contest.

“Today I feel like I was intimidated, she is playing well. I had to go within myself, I couldn’t play short balls to her because she’d put them away.”

Next up for Osaka is an all-Asian quarter-final against unorthodox 35-year-old Hsieh Su-wei of Chinese Taipei, who will be playing in the last eight of a Grand Slam for the first time.

Spain's Garbine Muguruza hits a forehand return to Japan's Naomi Osaka (not in frame) during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Feb 14, 2021. (HAMISH BLAIR / AP)

Although Osaka had never played Muguruza before, she had perhaps a better idea of what to expect from the former French Open and Wimbledon champion.

Muguruza, a finalist here last year, had conceded only 10 games in reaching the fourth round and continued that rich vein of form into Sunday’s match.

READ MORE: Nadal eases past Norrie into Australian Open last 16

Muguruza rued her missed opportunity but said she was happy overall with the start to her season.

Buglaria's Grigor Dimitrov hits a backhand return to Austria's Dominic Thiem (not in frame) during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Feb 14, 2021. (HAMISH BLAIR / AP)

Dimitrov stuns Thiem with straight wins

Over at the men's side, third seed Dominic Thiem slumped out in lackluster fashion, comprehensively beaten 6-4 6-4 6-0 in the fourth round by Bulgarian Grigor Dimitrov.

The US Open champion, who came back from two sets down to beat Nick Kyrgios in an exhausting third round battle on Friday night, looked out of sorts from the beginning of the contest and made an uncharacteristic 41 unforced errors.

While Thiem’s five-set match against Kyrgios had been played in a bear pit at John Cain Arena, Sunday’s match was witnessed by only a handful of officials and coaches on Rod Laver Arena as Melbourne’s coronavirus lockdown kept the fans away.

The first two sets followed the same pattern with Thiem taking an early 3-1 lead only for 18th seed Dimitrov to charge back at him and clinch the set.

Austria's Dominic Thiem reacts after a point against Bulgaria's Grigor Dimitrov (not in frame) during their fourth round match at the Australian Open tennis championships in Melbourne, Australia, Feb 14, 2021. (WILLIAM WEST / AFP)

The Austrian, losing finalist here last year, was unable to rouse himself in the third set and his Australian Open ended when he flapped a forehand long after little more than two hours on court.

“Throughout every season you have one of those matches where you keep the ball rolling,” Dimitrov said after going 4-2 up in his career record against Thiem.

“He might have had a problem, I don’t know, but I also give myself some credit for staying in there.

“He’s an extraordinary player so I’m happy with the win.”

Dimitrov will face Russian qualifier Aslan Karatsev in his fourth Australian Open quarter-final.