Anthony Joshua and Derek Chisora would have "no problem" in fighting each other despite their respectful relationship, says promoter Eddie Hearn.
Chisora would emerge as a threat to the world heavyweight champion if he can beat Usyk on May 23 at The O2 in London, live on Sky Sports Box Office.
Chisora and Joshua both progressed through the same amateur gym and continue to have a supportive rapport but their fighting instinct would come through if necessary, warned Hearn.
"They would fight. AJ is a massive admirer of Chisora. Growing up at Finchley, Chisora was a hero to AJ. But they will fight, no problem," Hearn told Sky Sports.
"It doesn't mean, if Chisora beats Usyk, he inherits the mandatory position. But he will become No 1 with the WBO and everybody will say: 'You deserve a shot at the world title'."
Usyk is the WBO mandatory challenger and would expect the next shot at the champion if he beats Chisora.
Joshua, meanwhile, will defend his titles against Kubrat Pulev on June 20, live on Sky Sports Box Office.
Chisora will get his first look at upcoming opponent Usyk at a press conference on Friday.
Ending Usyk's undefeated record would be a career-best victory for Chisora, the 41-fight veteran who has only once challenged for the world title.
Facing Chisora will be Usyk's second fight as a heavyweight - he was previously the undisputed cruiserweight champion and also owns an Olympic gold medal and the World Boxing Super Series winner's trophy.
"Usyk vs Chisora will be a thriller. Usyk is the undisputed cruiserweight champion but this is a different game," Hearn said. "If Chisora gets a hold of him, lean on him, slobber on him, this will be really difficult for Usyk.
"No none will match Usyk's feet or skill but does he punch hard enough in the heavyweight division to keep someone like Chisora, a lion, off him?
"People will automatically assume Usyk should win but if Chisora gets through the early rounds, and I don't see why he shouldn't, he will be heavy and work Usyk to the body.
"You saw a size difference and a strength difference [in Usyk's fight with Chazz Witherspoon]. He has been working on that.
"Chisora and [his manager] David Haye fancy this, and they can blow up the division if they win."