The comeback road has been a long one for Andy Murray but John McEnroe reckons the Scot is once again a leading contender for every Grand Slam tournament he plays.
The American believes Murray has improved by between 10 and 15 per cent since last summer, when he was still recovering from the back surgery he underwent at the end of 2013.
"He's in the top four at every Major he plays," McEnroe said.
"He has put himself back in the mix. It's taken him a while but he looks healthy and dangerous, and he has got respect. He is a threat. The way he has moved from a year or a year and a half ago, I would be surprised if he doesn't win a couple more Slams."
McEnroe, who will be part of the BBC's commentary team when Wimbledon starts on Monday, has been impressed with the way Murray has handled his coaching staff following his split with Ivan Lendl.
He appointed Amélie Mauresmo as his coach after last year's French Open and kept faith in her even though it took the Scot until this year to start beating the top players again.
Jonas Bjorkman joined Murray's entourage in April. The Swede has played an increasingly important role and will take full charge of Murray's coaching after Wimbledon. Mauresmo is expecting her first baby in August and is unlikely to return to coaching duties before the end of the year.
"I credit him for sticking with Amélie when it was looking like a lot of people were questioning it," McEnroe said.
"If you were going to start something right before Wimbledon (like Andy did last year), it felt like it was asking way too much of someone with the pressure of being defending champion. I think it was very smart of him to give it some time.
"Bjorkman does some things well which can help Andy, like being aggressive off the return, which he is doing more of anyway, volleying, positioning of where you are at the net. Those are important."
McEnroe thinks one of the only remaining areas for concern has been Murray's second serve - he would like to see the Scot put more first serves in court - but in other respects he has been impressed by the World No 3's improvement.
"I think overall he is 10 to 15 per cent better and that is a significant amount at his level," he said. "He is definitely feeling better about himself than he has done for a while.
"He is doing almost everything he needs to do, though I think his hands are good enough that he should use his skills at the net more often.
"He is starting to make that bigger impact off the return which is smart because he and Novak Djokovic are the best. Because he has such a sweet feel I think he should be in there at the net more.
"He's a big guy but he doesn't do that very often. That is the only thing I would tell him."
There has been talk for the last couple of years of younger players breaking through to challenge the 'Big Four' - Murray, Djokovic, Roger Federer and Rafael Nadal - but McEnroe believes it has become increasingly difficult to displace the men at the top.
"Roger is 33, soon to be 34, and he looks great, though it's tough when you get older to play best of five," McEnroe said. "Rafa has got some injury issues but I hope he's got another couple of years left in him."
McEnroe sympathised with Djokovic at the French Open, where the World No 1, under enormous pressure, ultimately failed to claim the last trophy missing from his Grand Slam collection as he attempted to emulate Federer and Nadal by winning all four Major titles.
"Join the crowd," McEnroe smiled. "In a way I was always thinking, 'How would I break in with (Jimmy) Connors and (Bjorn) Borg and be considered their equal?' It was not easy to do that and when I sort of felt like I was on that level, it felt like an amazing accomplishment.
"I think Novak's the same. He's got these two guys who are arguably the two greatest guys ever, but he's trying to be on an equal footing. And that's a hell of a tough thing to do when they have 17 and 14 Grand Slams and Novak's at eight.
"But he's got a chance to be considered one of the all-time greats if he keeps this up and keeps anything remotely close to what he's been doing. You've got to figure he's going to win at least a dozen Slams."
McEnroe has been pleased by the emergence of a much younger group of players, headed by Nick Kyrgios, Borna Coric, Thanasi Kokkinakis and Jack Sock, but believes it could be "a couple of years" before they started to challenge the Big Four on a regular basis.
"You have to have a good attitude and understand you are here for the long haul because these top guys are extremely professional," McEnroe said.
"They are very well prepared. It is a lot tougher these days, it seems to me, just based on people's understanding of recovery and what to do to maximise what you are doing on the court, including eating and everything else.
"It is a lot tougher to beat these guys in the Slams. They are like machines out there."
McEnroe singled out Kyrgios as the best of the new wave, though the Australian has had a difficult time in the last month and yesterday parted company with his coach, Todd Larkham.
"I think he would be the guy I would pick who could go all the way," McEnroe said when asked to choose one player from the next wave above all others.
"He is closest to being ready to make the big breakthrough."
McEnroe believes that characters like Kyrgios and Kokkinakis could give the sport a bright future.
"If all of a sudden these were the top couple of guys in the world, it could be a spark or a shot in the arm that we need," he said.
"You've got to make the sport cool in a way."
Wimbledon 2015 is exclusively live on the BBC across TV, radio and online from Monday June 29.