U.S. Open champion Dominic Thiem became the first major men's casualty of the Australian Open on Sunday, as Naomi Osaka and Serena Williams survived scares to reach the quarterfinals.
A fatigued-looking Thiem, last year’s runner-up and third seed coming off a five-set win over Australia's Nick Kyrgios, slumped in straight sets to Bulgaria's Grigor Dimitrov who took it 6-4, 6-4,6-0 in just over two hours.
Later, Novak Djokovic clocked his 300th Grand Slam win playing through pain from an abdominal injury that nearly forced him to pull out.
The World No. 1 battled on against giant Canadian Milos Raonic, grinding through 7-6(4), 4-6, 6-1, 6-4 to set up a clash with sixth seed Alexander Zverev.
But Djokovic said if it wasn't a Grand Slam, he would have pulled out.
Djokovic's win was his 300th at a Slam, only thesecond player in history to reach the mark after Roger Federer, on 362.
Close calls
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.
Second seed Simona Halep gained revenge over Iga Swiatek after her loss at last year's French Open. Halep won just three games against Swiatek, 19, at Roland Garros, but she turned it around with a 3-6, 6-1, 6-4 win.
Osaka was on the verge of elimination at 3-5, 15-40 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.
Serena, 39, was meeting Sabalenkafor the first time and she had to weather an onslaught from the Belarusian to reach the last eight 6-4, 2-6, 6-4.
Milestones
Taiwan's Hsieh Su-wei became the oldest player to make a last-eight debut in the Open era after winning 6-4, 6-2 against Czech Marketa Vondrousova.
Hsieh's reward is an all-Asian quarterfinal against Osaka on Tuesday.
Karatsev became the first player in 25 years to reach a quarterfinal on Grand Slam debut, stunning 20th seed Auger-Aliassime of Canada 3-6, 1-6, 6-3, 6-3, 6-4.
Alexander Zverev subdued Dusan Lajovic 6-4, 7-6 (7/5), 6-3 to bring up his 50th Grand Slam win.
