Chris Eubank Sr.'s "crazy demands" cost his son a £3 million fight against Gennady Golovkin, according to promoter Eddie Hearn.
World middleweight No. 1 Golovkin will instead defend his WBC, IBF and WBA belts against Sheffield's Kell Brook at the O2 Arena, London, on Sept. 10.
Golovkin (35-0, 32 KOs) had agreed terms to face Eubank Jr. (23-1, 18 KOs), but the Brighton boxer stalled on signing the contract and Hearn instead offered the fight to Sheffield's IBF world welterweight champion Brook (36-0, 25 KOs), who jumped at the opportunity.
Hearn blames Eubank Sr., the former world champion, for his son not landing the fight against Kazakhstan's California-based knockout specialist Golovkin, which included demands on which television commentator would work on the fight and how much tickets would cost.
"I believe Eubank Jr. genuinely wanted the fight and we worked solidly for three weeks trying to make the fight," Hearn told ESPN.
"We had several meetings and contracts went back in forth. We sent them a final contract on Tuesday and said you have 24 hours and they never came back to us. We just ran out of time, so I offered it to Kell.
"The deal that Kell Brook is on is the same as what Eubank Jr. was offered, it's the same same pay-per-view deal as Anthony Joshua is getting and what Carl Froch got.
"It was so frustrating. It was the crazy demands that meant the fight could not happen for Eubank Jr. against Golovkin. They think it's negotiations but it's not a bluff when I say it's 24 hours to sign the contract. They were given a deadline and they chose not to take the fight.
"They wanted full operational control of the promotion. They were even asking things from Sky Sports like 'We want these commentators', which is ridiculous.
"I feel for Eubank Jr. because I don't think he knows what's going on and he was going to earn three or five million pounds. They have to understand that it's not playing a game.
"Chris Eubank Jr. hasn't made one decision, he doesn't breathe without his dad's say so. All the negotiations were done with Chris Eubank Sr. and the lawyer.
He added: "They sent through their suggestion for ticket prices and I would have got publicly lynched if I had agreed to that."
Friday's surprise announcement has given Brook a chance to pull off a huge shock when he challenges the world No. 1 middleweight, who is ranked No. 2 in ESPN's pound-for-pound list.
GGG, as 34-year-old Golovkin is known, had been looking for an opponent since Mexican Saul 'Canelo' Alvarez pulled out of talks for a world title unification fight in September.
Golovkin has knocked out 32 of his 35 victims including Britons Matthew Macklin and Martin Murray, and will start as the overwhelming favourite against Brook, who will be stepping up two weight divisions just as his domestic rival Amir Khan did in May to fight Alvarez.
It is the big fight Brook has been craving since winning his IBF belt nearly two years ago, having since made three low-key defences.
Brook, 30, had been training in the Canary Islands expecting to fight American Jessie Vargas, the WBO champion, in a world welterweight title unification before Hearn made the offer to fight Golovkin.
It will be the biggest pay day of his career and Hearn has hailed Golovkin's UK visit as the biggest by an overseas boxer in years.
"Kell doesn't have to give up his IBF welterweight title and that was the defining decision if you like for him taking the fight because he has got nothing to lose and we believe he can beat Golovkin," Hearn said.
"If you are talking about fighters in their prime, when Mike Tyson and Kostya Tyszu came over they were past it, but Golovkin is very much in his prime."