Joshua was the long-term target for Usyk who wants to add the world heavyweight championship to his cruiserweight honours – he debuts in the top division against Chazz Witherspoon on Sunday morning at 2am, live on Sky Sports Action.
Joshua must first regain the belts that he lost to Andy Ruiz Jr in a rematch on December 7, live on Sky Sports Box Office, but would then find Usyk as the mandatory challenger to the WBO title.
“Joshua was excited when we signed Usyk, he was excited to see him in the heavyweight division,” said Hearn.
“Joshua saw Usyk a lot in the amateurs and he has never been scared to fight anybody, so he’d be up for fighting Usyk.
“Usyk is the mandatory but has to keep winning, and has to show that he is ready to fight [the champions] of the division.”
The winner of Ruiz Jr vs Joshua will face mandatory challenges from Usyk (WBO) and Kubrat Pulev (IBF) in 2020.
“It will be a mess,” said Hearn. “The belts are on the line in Saudi Arabia then the winner must decide what to do.
“But there is going to be a problem because mandatories are due with both organisations.”
The unbeaten Ukrainian Usyk “will definitely” have challenged for a world heavyweight title by the end of next year, Hearn believes.
“He will fight for the world heavyweight title in his next fight, if he beats [Witherspoon]. He wants to jump straight in. He thinks he can beat everybody.
“We’ll never really know until he’s in with the elite of the elite. Those four or five guys, big, big men that can really test him.
“I don’t know how easily he made cruiserweight, so maybe the extra stone will give him extra power. He won’t be the biggest punching heavyweight of all time but whatever he lacks (which won’t be much), he will make up for in skill.”
Usyk, last month, told Sky Sports that his dream fight was “Anthony Joshua at Wembley”.
He added: “I think it would be much harder for me to fight Joshua than Ruiz Jr. If you want to be the best, you have to fight the best.”
A year ago, Joshua warned: “Usyk needs to move up in the right stages, and figure out what it’s like being with 17 or 18 stone guys who can punch very hard.
“It’s not just based on skill, the heavyweight division. It’s based on will. How much you can take.
“I know he’s got amateur experience and has done well as a cruiserweight but if he moves up to the heavyweight division, it will also test his will as well as his skill.”