Tyson Fury might not "see 30 years old" if he is not helped back to health, his long-time friend Billy Joe Saunders says.
The world heavyweight champion, 28, appeared to announce his retirement on Monday only to issue a further statement claiming he was joking.
Fury has not fought since taking Wladimir Klitschko's WBA, WBO and IBF belts with a stunning points win in Germany in November 2015, and their latest scheduled rematch date was scrapped with the champion "medically unfit to fight".
There have also been unconfirmed allegations of a failed Voluntary Anti-Doping Association test, while Fury's uncle and trainer Peter Fury last month told Sky Sports his nephew was "very up and down".
Now middleweight Saunders, a fellow world champion from the travelling community, has gone public with his fears, saying: "I'm very concerned that he won't see 30 years old. Very concerned.
"If the public don't get behind him, and he doesn't get the help he needs, it could affect his life and his family's lives forever.
"The travelling community's behind him. But it's out of the travelling community - the press - that need to give him a breather, a pick-me-up, a pat on the back.
"I'm not saying everything he's done's right. Not even a 'You've done right, you've done wrong' - [he needs] 'It'll be alright, don't worry about it, chin up'. Give him a bit of that and perhaps he might see a little bit of light, it might give him a little bit of confidence.
"I've spoken to him, but he's down, he's very down, he's not in a mood to talk to anybody. He's mentally not there. Nothing shocks me at the moment, because he's not mentally right. He needs help. He's in a bad place at the minute. I know him very well; extremely bad place."
Fury said on Monday he is "getting the right help", adding: "I'll be back even stronger than before. Try and stop me."