David Haye believes Tyson Fury is "grossly overweight" and heading for defeat against Wladimir Klitschko in their rematch on July 9.
Former two-weight world champion Haye faces his second fight on Saturday since returning to the ring as he tries to win back a version of the world heavyweight title.
But Haye (27-2, 25 KOs) does not expect Fury to still be WBA-WBO world champion later this year.
"Fury has his own battle to take care of in the rematch with Klitschko and that fight is no foregone conclusion," said Haye, who stopped Aussie Mark De Mori in 132 seconds in January in his first fight in over three years.
"I believed it was a foregone conclusion until I saw Fury at the press conference. I assumed Fury would stay in camp but looking at the press conference it looked like he had completely taken his eye off the ball.
"Wladimir Klitschko won't have done that. Really, it was quite sad to see a young world champion looking grossly overweight. Ten weeks away, he shouldn't be worrying about losing weight but worrying about tactics, punches, angles, timing, rhythms, strategies.
"He's doing a Michael Douglas, who beat Mike Tyson and then ate himself into a diabetic coma. People will say you just flukes it. Fury could lose it if he loses the rematch."
Haye has defended the quality of his next two opponents, starting with Arnold Gjergjaj (29-0, 21 KOs). The Switzerland-based Kosovo-Albanian is largely unknown outside of his home city of Basel, where he works weekend shifts at his brother's grocery store.
It is not expected to be a competitive bout and Haye is already lining up 44-year-old American Shannon Briggs for September as his third opponent on the comeback trail.
"I think my opponents are the right standard," Haye told ESPN. "I've only had one round in the ring in four years so the next guy is unbeaten, young, big at 6 feet, 5 inches and has long arms.
"He's not fought any big names but that doesn't mean he would have beaten a big name. I don't really like to listen to the naysayers. I'm fighting an unbeaten guy, he's confident and it's perfect preparation and then i will look to a big fight with Shannon Briggs in September.
"Briggs is the biggest non-title fight out there. I want to give the public response to him, which is to shut this idiot up. If you ask British boxing fans to name a heavyweight other than the champions and me, it will be Shannon Briggs.
"I'm not looking to hang around with him. A September date would work for me, then I would have had three fights in a year. One of the biggest criticisms of me has been I've not had regular fights.
"I believe he [Briggs] has got a license and I think he has been licensed here as well. He's got a couple more medical tests."
For Haye, it is all about building towards a crack at British rival Anthony Joshua, who makes the first defence of his IBF world title against American Dominic Breazeale on June 25.
"The ideal situation is getting a big all British clash with Anthony Joshua next year," said Haye. "His promoter [Eddie Hearn] has said he would be interested in fighting me but not this year, which is understandable.
"I saw Anthony at an awards ceremony and I congratulated him on winning the world title and we said if we keep winning we will have a big fight next year. It's the fight everyone wants and it's all about next year at the moment."