Whyte will battle Alexander Povetkin on Saturday night, live on Sky Sports Box Office, and victory keeps him on course for a mandatory fight for Fury's WBC belt in early 2021.
Hearn says the Brixton man could even face Joshua in an undisputed world title fight, if Fury fails to fulfil his WBC duties, but the unified champion has told the Matchroom boss that he expects a stunning upset when he watches Whyte-Povetkin as part of the Sky Sports Box Office team.
"I know that AJ rates Dillian Whyte very highly, I know that Dillian Whyte rates AJ very highly, but they'll always be that fizz between them," Hearn told Sky Sports.
"I don't think AJ is the kind of guy to hope that Dillian Whyte will lose on Saturday. He actually, I think, believes that Alexander Povetkin will win on Saturday. I had a conversation with him the other day.
"This is a massive banana skin fight for Dillian Whyte. I don't think Tyson Fury really feels too deeply about it, but of course in boxing, there's so much bitterness."
Joshua overcame an early scare to stop Povetkin in the seventh round of their world title fight at Wembley in 2018.
But the WBA, IBF and WBO champion has suggested that Whyte can only triumph on points, if he has prepared correctly for Povetkin.