Klitschko had a clause in his contract with Joshua to allow him the chance to avenge his April loss, although the Ukrainian chose instead to retire.
This decision leaves Hearn looking at Joshua facing his mandatory challenger Kubrat Pulev despite rumors of a potential unification with Deontay Wilder.
Hearn knows he’s unlikely to gain a second exception from the IBF who already gave special dispensation for Joshua to defend his red belt against Klitsckho.
“When the IBF cleared the Klitschko rematch it was under the proviso that if it’s not Klitschko it must be Pulev, so we’ve already got talks in place with Kalle Sauerland,” Hearn told Sky Sports.
“Part of me is quite pleased we can move forward and draw a line under this. There was always the worry with Klitschko’s age that we could announce the fight and he could get injured in camp, various bits and pieces like that.
“At Anthony’s stage of his career, as young as he is, he’s really raring to go already. He’s been ticking over in the gym, he wants to start his camp and he’s been calling me every day saying ‘will he take the fight?’
“Now finally we’ve got an answer, so I think fight fans are going to see an announcement sooner than they would have seen with a Klitschko fight.
A venue scouting jaunt to Las Vegas recently could now turn out to be a wasted journey as Hearn mulls over a trip to Wales around the same time as he planned the Nevada Klitschko return.
“We need to sort out the final details but the venues don’t change. It will still be Vegas or Cardiff, with Cardiff probably the frontrunner,” Hearn told the Daily Mail.
“We have an agreement in place with the IBF that if it wasn’t Klitschko it would be Pulev. It will almost certainly be Pulev next,” he pointed out.
