Novak Djokovic took aim at Ben Shelton once again as the 21-year-old crashed out of the Australian Open in five sets. The pair were set to renew their rivalry in the round of 16 but Shelton fell to Adrian Mannarino.

Djokovic contested a fiery semi-final with Shelton at the US Open and has since admitted he mocked the American’s trademark phone celebration. And on Friday, he took more shots at the American’s behaviour moments after his defeat.

Djokovic booked his spot in the second week of the Australian Open on Friday, cruising past Tomas Etcheverry in straight sets. The world No. 1 awaited either Mannarino or Shelton, who were still locked in battle when Djokovic left the court. But it was Mannarino who came through after the tennis world had been eager to see a rematch between Djokovic and Shelton.

The 36-year-old beat the American at the US Open and copied Shelton’s trademark celebration from earlier in the tournament, pretending to hang up a phone. Their feud was long put to bed before the 24-time Major winner reignited it ahead of the Australian Open, telling L’Equipe that his opponent “did not behave correctly, with respect on the court, and also before the match.”

Djokovic was asked about Shelton ahead of a potential rematch, before the press conference moderator announced that the world No. 16 had just lost his match. But the 10-time Aussie Open champion still brought his rival up as he discussed turning negativity into fuel during matches. “As far as Shelton’s level of confidence and coming out, I don’t mind that actually at all. I think it’s great,” he said.

Djokovic was happy to see Shelton believe in himself, comparing the 21-year-old to his first-round Australian Open opponent, teenage qualifier Dino Prizmic. But the top seed rubbed salt into the wound of Shelton’s defeat as he took the opportunity to criticise his behaviour again.

He continued: “You got to believe. I’m all for that. I support 100 per cent a young player coming out on the court, like Prizmic did the other night against me, and Shelton is doing coming out believing in his capabilities that he can challenge the best players in the world. I don’t dislike that at all.

“But there is obviously some kind of line, non-visible line, of acceptable behavior I guess towards the other player. If a player steps over that line, then obviously it starts being annoying. That’s when you react or you don’t react, whatever. It just depends. But I’m all for young players showing confidence and speaking, always with respect, towards the older guys who are on the tour, but being confident in themselves and their tennis.”

Djokovic was happy to take any adversity in his stride, however, using it as fuel to perform better. “It was fueling me even more,” he said of negative comments from other players.

I mean, if I made a mistake, I would admit it and, of course, say I make a mistake, I raise my hand, I apologize or whatever. But if the criticism came with no particular reason I think, then I would just keep going the kind of direction that I chose, and that’s it.

“I knew and I know today that you can’t have everyone liking you, who you are, how you play, how you behave, what you talk about. It’s normal. We’re all different. We are all different preferences.”