Joshua could face Wladimir Klitschko in late November or early December but there had been speculation that Haye was in the running to take on the Olympic gold medallist after revealing the date for his return to action.
However, while the pair could both compete on December 10, Hearn says they will not be fighting each other.
The Matchroom Sport chief told Sky Sports News: "He's not fighting AJ but there are rumours he might go the same night.
"I think that's a fight that's not too far away either but the Klitschko fight is the one that really whets the appetite."
Hearn is hopeful of confirming the showdown between Joshua and Klitschko by the end of the week.