"Bernard has got more upside than any young guy I see out there," McEnroe told reporters in Adelaide on Monday. "He has developed a great deal. He's a very savvy player for a young kid.

"He's going to get stronger. That will help him ... he is right there with the young guys as one who can make the breakthrough and win some majors."

McEnroe also appealed for Australian stalwart Lleyton Hewitt to be allowed a farewell on his own terms.

"Lleyton is going to be in the Hall of Fame. He's one of the gutsiest ever players, he's in the top five," McEnroe said.

"And he's pretty darn talented to be 5'11 and standing up to the guys for as long as he did. It's amazing.

"But his body took a real beating. He should be entitled to play as long as he wants to play. He deserves that.

"I can only imagine what he has gone through to give himself a chance to even play.

"He's an incredible competitor and I suspect he wants to go out on his terms."

McEnroe, who will contest the World Tennis Challenge in Adelaide from Tuesday, said he would be a fascinated watcher of Ivan Lendl's coaching stint with Scot Andy Murray.

"I hate to give credit to Lendl," McEnroe said of his old-time rival.

"But he (Murray) needed to do something out of the ordinary instead of going with the predictable re-tread.

"This is definitely something that was, to me, unexpected.

"I didn't know that Lendl wanted to coach. He could bring something to the table, without a doubt. Lendl didn't win a major until he was 24 and guess what, Murray is 24 right now.

"So that could provide something worth it for Murray. I'm going to be paying attention to that, see how it works out."

McEnroe, while tipping Novak Djokovic to win the Australian Open, also believed Roger Federer would win more majors.

"I think he has one or two left in him ... I would be surprised if he didn't win another one," he said.