0612 GMT October 17, 2021
The Serb currently has 16 Grand Slam titles to his name, behind only his two great rivals in the all-time rankings, with Nadal on 19 and Federer on 20, Eurosport reported.
McEnroe believes that Nadal could equal or surpass the Swiss veteran by the end of the year but that Djokovic will ultimately end up with the all-time record.
"At the end of the year it would obviously Rafa or Roger but if you ask as a betting man I’d probably lean towards Novak," he told Eurosport.
"If he stays healthy over the next couple of years you could see him winning a couple each year and he’ll be there and then you have to wonder whether Roger could win another one and whether or not anyone will ever beat Rafa at the French.
"You would think what we’ve been watching in the last couple of years that right now it still looks very likely that Rafa is going to win another French, at least one, and could pull off something else and that could put him past Roger and potentially this year if he stays healthy."
McEnroe is also backing Djokovic to continue his pursuit of Federer's record at the Australian Open, beginning on Monday, but is hoping one of the ATP's younger stars can make a breakthrough in Melbourne.
"Djokovic has to be the favorite. I think it would be exciting for the day, these guys are legends obviously, to see a younger guy play through; I think [Daniil] Medvedev is the best shot at it, he seems to have positioned himself and got the confidence and belief.
"Novak obviously has won it seven times, so it can’t be that easy to keep winning it. So it’s going to be interesting to see if one of the young guns makes the breakthrough this year."
Djokovic has won seven Australian Opens, more than any man in the tournament's history but McEnroe is at a loss to explain why the 32-year-old enjoys playing in Melbourne so much.
"It’s hard to say. Obviously he’s had a lot of success at the other events – Wimbledon he’s won numerous times and the US Open, I think hard courts to me would be his best surface, but I think he gets a lot of support which makes him feel good there, more so than almost any other major, I think that fires him up, it helps him.
"I wish I knew because that’s always the issue, coming in when you haven’t played for a while or trying to train and get ready when there’s not much of an off-season but he’s done an amazing job when you look at his record.
"So whatever he’s doing, I’m sure there’s a lot of other players that wish they could bottle the same thing. But let’s face it, he’s one of the all-time great players so if he gets his head in the right space and he’s physically ready, best of five, it is a very tall order to beat him. He’s just so solid, he’s like a human backboard."