JOHN McEnroe fears Nick Kyrgios's volcanic mentality is as much of a liability as the Australian's wonky left hip ahead of the start of Wimbledon on Monday night.
With Kyrgios labouring under injury, triple All England Club champion McEnroe fears his penchant for implosion might re-emerge.
Asked to assess Kyrgios, McEnroe said "Unpredictable.
"I think his best chance of winning something big would be here, but he doesn't seem if mentally he's ready yet.
"I mean, everything's there but he's been injured, too.
"So that makes him pretty much an unknown quantity but this should be his best chance.
"This guy has the most talent, out and out tennis talent and physical attributes of anyone out there.
"I'm sure there's a lot of people who'd want to get their hands on him because he could be the best player in the world.”
Kyrgios faces Frenchman Pierre-Hugues Herbert in the opening round, but McEnroe says the 20th seed will struggle unless he fully commits - injured or not.
"In terms of talent, he's got an incredible amount but I'm not gonna put him with Roger Federer, the greatest player who's ever lived, and (Rafael) Nadal,” McEnroe said.
"Talent is mental strength and talent is physical strength. It's not just how well you hit the ball or how hard you serve or how well you move on court.
"It's a combination of things. Nick's talent is as good as anyone.
"I'm just hoping and praying because I've seen evidence where there are times when he just doesn't like it (competition), or seem to want to embrace it, or he hasn't prepared well enough.
Kyrgios revealed he is at between 60-65 percent fitness.
"It's not great. I played a couple of matches at Boodles (exhibition) the last couple of days to see where I was at and it's definitely not 100 per cent,” Kyrgios said.
"But I'm still gonna obviously feel confident on the grass.
"I can serve well and still be successful but, at the same time, it's not where I'd like my body to be.”
Kyrgios won two exhibition matches at Stoke Park, but conceded: "I didn't play hard at all at the Boodles.
"I think that's why I wanted to play there. It's a very controlled environment.
"Both players sort of know you just want to feel the ball, you don't want to go too hard.
"I'll be doing absolutely everything I can.
"I've been taking anti-inflammatories, doing an hour and a half of rehab every day, getting treatment.
"But there's only so much treatment I can do with type of injury.
"It needs time to rest.
"I was in a good place before Queen's.
"I got an injection after Paris, took 10 days off, rehabbed it and then slipped on the grass in Queen's which kinda screwed everything up, I guess.”
A quarter-finalist here in 2014 and a fourth-round presence for the past two years, Kyrgios said a bone bruise in his left hip impacts "pretty much everything.”
Kyrgios, John Millman and Andrew Whittington lead the Australian charge on the opening day.
Millman takes on world No 2 and fourth seed Rafael Nadal.
Whittington plays Brazil's Thiago Monteiro.