Anthony Joshua must be "ruthless" to battle past "tricky and difficult" Oleksandr Usyk, his promoter Eddie Hearn has warned.
Joshua is set to defend his IBF, WBA and WBO heavyweight championships against his mandatory challenger Usyk in September at the Tottenham Hotspur Stadium in London.
Tyson Fury and Deontay Wilder will, meanwhile, meet for a third WBC title fight on July 24 in Las Vegas.
Hearn told Sky Sports about Joshua's plans after the breakdown in his proposed fight with Fury: "We have both alerted the WBO, myself and (Usyk's promoter) Alex Krassyuk.
"Terms are agreed. The offer we made to them has been accepted.
"We move forward to paper that now. We are going through the contract with their team.
"It is very amicable. They have been partners of ours for a long time.
"This is a fight that could derail the career of Joshua if he's not on it, if he's not 100 per cent.
"AJ needs to be ruthless. He needs to show the [ruthlessness of] Derek Chisora with more cuteness and sharpness."
Joshua and Usyk were both Olympic gold medallists at London 2012.
The undefeated Ukrainian went on to become undisputed cruiserweight champion and has now stepped up a weight class.
"Usyk just wants the fight, he wants the opportunity to become heavyweight champion," Hearn said.
"[Joshua] loves the fight. We all know it's tricky, we all know it's difficult.
"But what else are we going to do?
"AJ is a throwback fighter and, for years and years, has faced all of the people that [were made his mandatory challengers].
"Time and time again, AJ has never shirked a challenge.
"And this is a real challenge. Look at the pound-for-pound top-10 list, AJ is not on it. Usyk is.
"AJ wants to make a statement, these are the fights that he likes."
Joshua, in 2018, told Sky Sports about Usyk: "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."