The Russian fourth seed was too strong on Saturday night for the young Australian, who was hampered by a leg issue, winning 6-4 6-3 6-2.

Medvedev will take on three-time grand slam champion Stan Wawrinka for a place in the quarter-finals.

He has a perfect 2-0 record against the Swiss veteran, with victories at last year's US Open and in 2017 at Wimbledon.

"A very tough opponent for a fourth round. Stan always plays good in majors, even when he's not in his best shape," Medvedev said.

While his third-round victory seemed comfortable, the 23-year-old said it was far from that.

Popyrin received medical attention several times during the match and was clearly hampered.

It seemed as if the Australian might retire when he went off for an extended medical timeout at the end of the second set, but Popyrin battled through the pain barrier until the end.

"It was a great match, especially playing against Alexei - it's not easy," Medvedev said.

"To be honest, I have no expectations (for the tournament).

"Every time I lose a match, I'm super disappointed. I just try to win as many matches as I can."

Russia might have as many as three men through to the round of 16 after Andrey Rublev's upset of 11th seed David Goffin.

Karen Khachanov was also locked in a third-round battle late on Saturday night with Australian Nick Kyrgios.

Medvedev said it was great for Russian tennis, Khachanov also playing well at Melbourne Park.

"We have all known each other since we were nine, 10 (years old)," he said of the trio's relationship.

Australian Associated Press