Joshua is set to defend his WBA, WBO, IBF and IBO titles against Ruiz in New York on June 1.
After that, the Brit’s team will attempt to reopen negotiations with Wilder’s camp over a blockbuster unification bout.
However, if the pair are unable to come to an agreement then will go to their contingency plan.
Joshua will turn his attention to IBF mandatory Kubrat Pulev and WBO mandatory Oleksandre Usyk if Wilder remains coy.
“He has got to take care of all of his mandatories,” Hearn told iFL TV.
“He has got Usyk as a mandatory. He has got Pulev as a mandatory.
“Again, they are decent fights but they are not Wilder.
”If Wilder will not fight then you have got to take care of your mandatories.
“He also liked the [Luis] Ortiz fight but if he is fighting Wilder then it is unlikely.”
There is talk that Wilder has already got his next two fights pencilled in, against Luis Ortiz and Adam Kownacki.
“Why would you do that?” Hearn quizzed.
“Why would you want to rematch Luis Ortiz when you can fight Anthony Joshua for three times the money?
“Why would you plan to fight Adam Kownacki?
“People might say that Andy Ruiz is of a similar level to Adam Kownacki.
“Andy Ruiz came in a six weeks notice.”