Joshua and Fury are both in action this week against Kristian Prenga and Mariusz Wach respectively, as they warm up for their planned blockbuster bout later this year, and the promoter was angered by Fury's claim that he has lined up a fight with "somebody else" as he fears his rival may withdraw.
Hearn told Sky Sports: "Look at history. Check the facts, check the resume. If you really want to pick one fighter who's more reliable than the other, I don't think it's a close-run race.
"What fight has AJ ever signed for that he's not competed in? What fight has AJ ever pulled out of?
"He's got the most solid resume and the most professional attitude of any fighter I've ever worked with. Can we say the same about Tyson Fury? No. That's the reality of the situation.
"If odds are being thrown around about who might pull out of this fight, trust me, it isn't Anthony Joshua.
"Don't forget, AJ has not only fought every contender he could have, he also previously signed to fight Tyson Fury, who pulled out of the fight because of an arbitration ruling involving Deontay Wilder.
"So don't worry about AJ, he's as game as they come. But we have our doubts about whether Fury will turn up, especially if AJ looks great on Saturday (25.07.26) night (against Prenga)."
Hearn suspects that Fury's comments are an example of the former world champion trying to play mind games with Joshua ahead of the bout, which is expected to take place in November should both win their tune-up fights.
The Matchroom chief said: "This build-up is going to be epic. We know the fight is going to be epic. In and out of the ring, this is going to be box office. We've waited a long time for this.
"It's going to be spicy, funny and compelling. Two very different characters. God willing they both get the wins on Friday and Saturday and we can finally get this thing on.
"There will be mind games. Fury is the self-professed king of those and he's very good at it as well. Fury will think he can win the fight that way, before the first bell, but I think he will be very disappointed. AJ is mature enough to deal with that now."
