Fury has not boxed since famously defeating Wladimir Klitschko in November 2015, and has battled mental health problems and a lengthy saga with UKAD since.
The British Boxing Board of Control granted the 29-year-old clearance to resume his boxing career last year when he accepted a backdated two-year doping ban, and he is aiming to return to the ring in the spring, but his friend Hatton is unsure whether he will recapture his former glory.
"The worry is how much Tyson has left in him," the Daily Mail quotes Hatton as saying.
"If Tyson had fought Anthony Joshua within five or six months after that win over Klitschko then I believe he would have won. Maybe knocked AJ out if he caught him with a big shot.
"But it's been a long time out and I'm not sure he can be that man again. I would love to see him back at his best in the ring but although he is still young it won't be easy."
Fury is training at Hatton's gym in a bid to get back into shape ahead of his comeback, and is said to have shed around four stone since he resumed training.