OSAKA, WILLIAMS FIGHT ON

In an empty Rod Laver Arena, with fans barred on the second day of a five-day, state-wide coronavirus lockdown, Osaka was on the verge of elimination at 3-5, 15-40 on her serve in the third set.

But the three-time major champion rattled off four points in a row and then twice broke Muguruza's serve to prevail 4-6, 6-4, 7-5. 

"I felt like I was intimidated because she was playing so well," said Osaka, after her first meeting with last year's beaten finalist.

"On the stressful points, I had to play within myself."  

Osaka now faces an all-Asian quarterfinal with Hsieh, who beat Marketa Vondrousova 6-4, 6-2 to reach her first Slam quarterfinal in 16 years of trying.

Williams, 39, was also meeting Sabalenka for the first time and she had to weather an onslaught from the Belarusian to reach the last eight 6-4, 2-6, 6-4.

"I knew it wasn't going to be easy, she was teeing off on every shot," said the American, who will play Halep in the quarterfinals.

But a fatigued-looking Thiem, coming off a five-set win over Australia's Nick Kyrgios, slumped in straight sets to Dimitrov who took it 6-4, 6-4, 6-0 in just over two hours.

Dimitrov's victory against Thiem, the third seed and last year's runner-up, sets up a quarterfinal with surprise package Aslan Karatsev, who is into the last eight on his Grand Slam debut.

"Whether it's a fairytale or not, it's a match and you've got to be ready," Bulgaria's Dimitrov said of the unheralded Russian.

"I've seen a little bit of his matches, clearly he's a dangerous player."

Karatsev beat Felix Auger-Aliassime in five sets to become the first player in 25 years to reach the quarterfinals on his Grand Slam debut.

The 27-year-old, a virtual unknown before the tournament started, battled back from two sets down to upset the Canadian 3-6, 1-6, 6-3, 6-3, 6-4.

Halep won just three games against Swiatek, 19, at last year's Roland Garros, but she turned the tables with a 3-6, 6-1, 6-4 win.

"I knew she would hit strong, but after the first set I tried to make her run and she started to miss," said the Romanian. (AFP)