The 32-year-old will attempt to win back his world title belts for the second time when facing the Ukrainian in Saudi Arabia next month.
A potential unification fight with Tyson Fury could present itself to Joshua if he can secure the victory, but former champion Haye reckons defeat could spell the end of his fighting career.
“If he doesn't win, I am not sure AJ wants to be in a sport where he knows he is not the best,” said the 41-year-old.
“He got out-hustled by someone he knows he can beat; he just got it wrong. If he brings a great game plan, and does everything he's supposed to do to beat Usyk, and Usyk still beats him, then what more is there to do?
“He's then not number one. He is such a winner... does he regroup? I'm not sure. At the moment he believes he has all capabilities to beat Usyk, and I think physically he has. All he needs to do is tactically get it right and he should be able to beat Usyk.
“Hopefully his team give him the right instructions, and he can go out there and fulfil what most of us believe is his destiny.”