Novak Djokovic was unhappy with himself for losing his temper as he dropped his first set of the Australian Open against Denis Shapovalov.

The world number one lost five straight games from 4-1 up in the third set but responded emphatically to win 6-3 6-4 4-6 6-0, thereby guaranteeing he will stay top of the rankings after the tournament.

Djokovic was unhappy that the floodlights were put on during the third set and that appeared to affect his focus. At set-point down, he was given a code violation for swearing from umpire Damien Dumusois, responding with a sarcastic thumbs up.

"I misconducted myself verbally," was Djokovic's euphemistic description for his moment of anger.

Of his overall performance, Djokovic said: "Other than the little letdown that I had when I was 4-1, 4-2 up in the third set, I thought I played well, especially in the fourth set.

"I expected Denis to come out and be aggressive. He made a lot of unforced errors, I thought, for the first set and a half.

"I just stayed solid from the back of the court and served well, played the right shots. For the first two sets, I just had things under control.

"At 4-1, I was agitated. It should not happen to me. I know better. I have experience. But it does happen, I guess. I allowed him to come back into the match.

"It was important to start off the fourth set well. But I like the fact that I was tested, as well, because you want to be tested. Matches and opponents are going to get tougher. I feel like I've been playing well, so things are progressing well."

Regarding the issue with the lights, Djokovic said: "I just felt with such a low position of the sun, the lights being switched on at 5pm was completely unnecessary. It was very bright.

"But the explanation that I got from the supervisor was that TV requested that. Whatever TV says, we have to respect I guess."

It was a first meeting between Djokovic and 19-year-old Canadian Shapovalov, who is one of the most exciting talents among the next generation.

Djokovic was impressed, saying: "He's got a pretty complete game. He's got the big serve, a lot of rotation on the ball. He can hit it flat. He can hit it with a spin. I like his mentality. I like his confidence in himself.

"Obviously he's lacking some experience playing on the big stage in the big matches, but that's going to come. These kind of experiences can only help him."

Shapovalov said with a smile: "He's good. I think he's number one good. But I had my chances, definitely. Especially after the third set, I felt a little bit physically dead. He started the fourth really well.

"But the first two, it was a little bit difficult for me in terms of it's not every day I'm playing a match against a top guy like this on a stage like that. Definitely I was a little bit nervous, a little bit tight on everything."

The two exchanged warm words at the net, with Shapovalov adding: "He just told me it's a pleasure to play against me. Honestly the pleasure was all mine. To play a champion like him in a court like that in an event like this, it's a dream come true for me.

"During the match, I was smiling, enjoying my time out there. It was a lot of fun. At the same time I do want to compete against these guys in the future, in the near future. It's about physically getting ready for these types of matches."

Djokovic will next play another young gun in Russia's Daniil Medvedev, who is through to the last 16 at a slam for the first time after beating David Goffin in straight sets.

Fourth seed Alexander Zverev also breached new ground in Melbourne, seeing off Australian wild card Alex Bolt 6-3 6-3 6-2. He will next face Milos Raonic while Kei Nishikori, Borna Coric and Pablo Carreno Busta also won.