The Serbian legend has failed to win a major title in a year for the first time since 2017 after his early exit at the US Open but the tennis great expects the Olympic champion to "find his motivation again" to contend for the biggest prizes in 2025.

McEnroe told Eurosport: "You never want to count him out.

"This would certainly be the first time where you could say with some seriousness that you start to wonder if he's going to win again.

"How long can this guy keep motivated? Then he won the Olympic gold. I'm amazed that he's kept it [motivation] for this long."

McEnroe does think it will be more difficult for 24-time Slam winner Djokovic to reach his previous level as he no longer has the "fear factor" against talented youngsters such as Carlos Alcaraz and Jannik Sinner.

The former Wimbledon champion said: "I'm sure to be surprised either way. If he doesn't win [a major], you would be like wow – he won three of the four last year. And now we're saying he'll never win it again.

"And then I would sort of be surprised in a way if he did, because his age. At some point, that catches up to you, and you lose a little bit of that fear factor with some of the guys.

"Then guys that didn't think they had a chance feel like they have a chance, and that whole thing changes and makes it much tougher.

"That's what he's facing right now. It will be interesting to see if he's able to pull it off. But I do think he'll try to find that motivation to get number 25."