The Russian overcame some serving woes to score a 6-3 4-6 6-4 6-2 win over world No.50 Tiafoe, who was a Open quarter-finalist at Melbourne Park last year.

Medvedev, who lost the 2019 US Open final in a tough five-setter to Rafael Nadal, is looking to improve on a fourth round showing last year which was his best effort in three trips to Melbourne.

He's ear-marked as one of the players to lead when Nadal, Roger Federer and Novak Djokovic finally call it quits.

The 23-year-old fourth seed was strangely out of sorts with his serve - tallying 12 for the match including six in the final sets despite the dominant scoreline.

"I think I have a lot of things to improve regarding today's match," Medvedev said.

"Especially the serve, I was not happy at all with my serve."

Medvedev has had an impressive start to the year, winning four ATP Cup singles ties before running into world No.2 Djokovic in the semi-finals.

But he still felt he needed to find his feet in the cool conditions at Rod Laver Arena.

"Today was not hot and the ball was not going so fast and for me it's a little bit tough to accelerate the ball.

"When I lost the second set, I knew I had to be more aggressive because he started pushing me all over the court and it worked well.

"The most important is just win the match, get into the second round, get the sensations of the court, of the atmosphere, everything.

"Usually later in the tournament everything goes better and better."

He next takes on Spanish qualifier Pedro Martinez.

Australian Associated Press