Novak Djokovic's straight-sets victory over Cameron Norrie in the Italian Open boiled over when the British tennis star hit the back of the world No. 1's leg with a smash.

The incident occurred at the start of the second set and despite an instant apology from Norrie, Djokovic did not respond well, proceeding to stare down his opponent.

The stare from Djokovic kept going as he walked towards the net before offering a verbal rebuttal to the British No. 1.

"Maybe you could say he didn't hit me deliberately," Djokovic told reporters after his 6-3 6-4 win in the round of 16.

"I don't know if he saw me. I mean ... you can always see where the player is positioned on the court."

Djokovic added that he wasn't altogether enamored with Norrie's behavior in general throughout the match.

"It was not so much maybe about that, but it was maybe a combination of things," said the 35-year-old Djokovic.

"He was doing all the things that we're allowed. He's allowed to take a medical timeout. He's allowed to hit a player. He's allowed to say 'come on' in the face more or less every single point from basically first game.

"Those are the things that we players know in the locker room it's not fair play, it's not how we treat each other. But, again, it's allowed."

However, Djokovic didn't let his unhappiness with Norrie impact his form on the court as he eased towards a place in the Italian Open quarterfinals.

"He brought the fire, and I responded to that. I'm not going to allow someone behaving like this just bending my head. I'm going to respond to that," added the 22-time grand slam winner.

"I got along with Cameron really well all these years that he's been on the tour. Practised with each other. He's a very nice guy off the court, so I don't understand this kind of attitude on the court, to be honest."

Norrie's representative didn't immediately respond to CNN's request for comment.