Djokovic passes Medvedev test to make Melbourne last-eight

Novak Djokovic struck back for the old guard at the Australian Open on Monday, soaking up the pressure from a willing Daniil Medvedev before crushing the young Russian 6-4 6-7(5) 6-2 6-3 to reach his 10th quarter-final at Melbourne Park.

The night after Roger Federer was stunned by Greek tyro Stefanos Tsitsipas, there was another sniff of an upset at Rod Laver Arena as 22-year-old Medvedev rocked the Serb with a furious assault of power hitting.

Yet the Russian wearied in the constant attrition, and top seed Djokovic cruised to victory, having passed easily his biggest test at the tournament.

The world number one will continue his bid for a hat-trick of Grand Slam titles and a record seventh at Melbourne Park against eighth seed Kei Nishikori. 

Highlights from Day 8

Serena Williams ended world number one Simona Halep's run at the Australian Open on Monday, surviving a second set fightback from the Romanian to keep alive her hopes of winning a first Grand Slam since becoming a mother.

Williams' 6-1 4-6 6-4 victory set up a quarter-final meeting with big-serving Czech seventh seed Karolina Pliskova and kept the 37-year-old on track to equal Australian Margaret Court's all-time record of 24 Grand Slam titles.

"She's always someone that comes out and serves big and plays well," Williams said of her next opponent. "I've got to return a little bit better the next day that we play, but I will be ready. She's ready, I'm ready, and let's do it."

Japanese fourth seed Naomi Osaka, one of four players who could oust Halep as world number one at the end of the tournament, ground out a 4-6 6-3 6-4 victory over U.S. Open semi-finalist Anastasija Sevastova.

Tempers frayed in the men's draw, with fourth seed Alexander Zverev smashing his racket and Spain's Pablo Carreno Busta flinging his kit bag across the court in frustration as they both bowed out in contrasting fashion.

Zverev was beaten by clinical Canadian Milos Raonic in straight sets while Carreno Busta went down fighting 6-7(8) 4-6 7-6(4) 6-4 7-6(8) in a five-hour marathon against Japanese battler Kei Nishikori.