Eight-time winner Novak Djokovic fought through what he had described as a tournament-ending injury to beat Milos Raonic and reach the Australian Open quarter-final Sunday.
Naomi Osaka and Serena Williams survived scares to go through but US Open champion Dominic Thiem was a major casualty when he fell to Bulgaria's Grigor Dimitrov.
Simona Halep avenged her crushing French Open defeat by Polish teenager Iga Swiatek to set up a meeting with Williams, while Taiwan's Hsieh Su-wei reached her first Slam quarter-final at the age of 35.
Djokovic, the world No 1, had raised the alarm over an abdominal injury after his five-set battle with Taylor Fritz, but he showed few outward signs in his 7-6 (7/4), 4-6, 6-1, 6-4 win.
However, the 17-time Grand Slam winner said he had spent "every single hour" since Friday's win trying to recover, and wasn't sure he would play until he warmed up before the match.
Djokovic becomes just the second player after Roger Federer to win 300 Grand Slam matches.
Rafael Nadal stayed on course for a record 21st Grand Slam title at a fan-free Australian Open Saturday as Ashleigh Barty gave locked-down Melbourne something to cheer.
Posted by Sports Tribune on Saturday, 13 February 2021
The defending champion will next meet German sixth seed Alexander Zverev, who beat Serbia's Dusan Lajovic 6-4, 7-6 (7/5), 6-3 as he seeks his first Grand Slam title.
Earlier, Japan's Osaka edged a thriller with fellow major-winner Garbine Muguruza, and Williams came through a physical test against Aryna Sabalenka to maintain her bid for a record-equalling 24th Grand Slam title.
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.
This was Osaka’s first meeting with last year's beaten finalist.
Osaka now faces an all-Asian quarter-final with Hsieh, who beat Marketa Vondrousova 6-4, 6-2 to reach her first Slam quarter-final in 16 years of trying.
Defending champion Novak Djokovic admitted his Australian Open might be over after an injury-hit win Friday as fans were kicked out ahead of a state-wide coronavirus lockdown.
Posted by Sports Tribune on Friday, 12 February 2021
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.
The American will play Halep in the quarter-final.
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 quarter-final with surprise package Aslan Karatsev, who is into the last eight on his Grand Slam debut.
Karatsev beat Felix Auger-Aliassime in five sets to become the first player in 25 years to reach the quarter-final 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.