The tit-for-tat between Kyrgios and the world No.1 has escalated in recent days.

Kyrgios labelled Djokovic a "tool" for writing a list of player demands during the hotel quarantine period leading up to the Australian Open.

He was also critical of Djokovic for hosting an exhibition tournament in June during the height of the COVID-19 pandemic, which resulted in the world No.1 and a host of other players testing positive.

On the eve of the Australian Open, Djokovic said Kyrgios was good for the sport but he didn't respect him off the court.

Those comments confused Kyrgios, who said, if anything, Djokovic should respect him off the court, rather than on it.

"It's a strange one for me," Kyrgios said.

"It actually would make complete sense to me if he was like, 'Look, I don't respect the guy on the court', because I understand if he doesn't agree with some of my antics on the court that I have done in the past.

"But I'm not quite sure how he can't respect me off the court. I feel like I've gone about things extremely well, especially during the pandemic.

"I was driving around delivering food to people during the pandemic. I was extremely careful about what I was doing. I didn't want to spread the virus to anyone.

"Now I'm actually trying to donate meal kits to people that need food. I have my foundation.

"So it's very strange to me as why he would say he doesn't respect me off the court. I actually do a lot off the court.

"But yeah, he's a very strange cat, Novak is. Heck of a tennis player, but unfortunately someone that's partying with his shirt off during a global pandemic. I don't know if I can take any slack from that man.

"That's as bad as it gets for me."

Djokovic didn't want to add more fuel to the fire when told of Kyrgios' comments.

"You can read it, but I'm not going to answer to anything," Djokovic said.

Kyrgios was also asked who, out of Djokovic, Roger Federer, and Rafael Nadal, was the greatest.

"In my opinion, I believe Roger is the greatest of all-time," Kyrgios said.

"With his skill set, the way he plays the game, I think it's pure.

"I actually think, talent-wise, Nadal and Djokovic aren't even close to Roger.

"Talent-wise, just purely based on talent the way Federer plays, his hands, his serving, his volleys - untouchable."

Kyrgios kicked off his Australian Open campaign with a 6-4 6-4 6-4 win over Frederico Ferreira Silva on Monday night.

The result sets up a tricky second-round clash with world No.34 Frenchman Ugo Humbert.

Australian Associated Press