Rafael Nadal acknowledged he had displayed "caution" in his straightforward first-round win over Hugo Dellien at the Australian Open, while Daniil Medvedev tasted victory in his opening match.

World number one Nadal eased to a 6-2 6-3 6-0 victory in just over two hours at Rod Laver Arena, hitting 38 winners to 21 unforced errors.

Nadal, who had his serve broken twice, stepped it up a gear in a ruthless third set, but initially was more focused on not making any silly mistakes.

"It was a solid start," Nadal said after booking a round-two match against Federico Delbonis, who won his match with Joao Sousa.

"The third set was a great set, I think I played a very good level of tennis. The first two I played with a little bit more caution. 

"I was just trying to not do something very good, but not do something very bad. Just trying to play a solid game with not many mistakes. Just try to do the things I know that I can do, try to put myself on rhythm. 

"That was my goal at the beginning of the match. Then, of course, with an advantage on the score, I just tried to play the way that I really believe I need to play if I want to have a positive result here."

MEDVEDEV THROUGH AFTER TIAFOE SCARE

Fourth seed Medvedev dropped a set against Frances Tiafoe but ultimately prevailed 6-3 4-6 6-4 6-2 in two hours and 36 minutes.

World number five Dominic Thiem made an impressive start with a 6-3 7-5 6-2 victory over Adrian Mannarino.

Home hope Nick Kyrgios won two tie-breaks on his way to a win in his match with Lorenzo Sonego, coming out on top 6-2 7-6 (7-3) 7-6 (7-1), while Gael Monfils and Andrey Rublev progressed into round two.

After his troubling performance at the ATP Cup, Alexander Zverev made a positive start in Melbourne with a 6-4 7-6 (7-4) 6-3 victory against Italian Marco Cecchinato.

ANOTHER CANADIAN STAR FALLS

After Denis Shapovalov fell on day one, 20th seed Felix Auger-Aliassime succumbed to a stunning defeat on Tuesday.

He was beaten by Latvian veteran Ernests Gulbis, who emerged a 7-5 4-6 7-6 (7-4) 6-4 winner after three hours and 35 minutes.

"Every time you come to Australia the main goal is the Aussie Open, so it's not good," Auger-Aliassime said. 

"That’s what the results show. But at the same time I am staying calm and positive because I feel I am not far from playing well and winning matches."

Jo-Wilfried Tsonga, the 28th seed, is also out. He pulled out with a back injury while two sets to one down against Australian Alexei Popyrin.

FOGNINI MAKES DRAMATIC ESCAPE

Fabio Fognini started Tuesday two sets down against American Reilly Opelka, but the Italian turned it around to escape with a dramatic 3-6 6-7 (3-7) 6-4 6-3 7-6 (10-5) victory.

In the other matches that had to be completed on day two after rain delays on Monday, Roberto Bautista Agut beat Feliciano Lopez in straight sets, while Milos Raonic and Jannik Sinner also sealed their progress with straight-set wins.