Amir Khan will now face Billy Dib in Saudi Arabia on July 12 after original opponent Neeraj Goyat suffered "severe injuries" in a card crash.
The Indian pro boxer was set to take on former world champion Khan for the WBC Pearl World Championship in Jeddah.
But he suffered head, face and left arm injuries in an accident whilst travelling back from training in his homeland.
Bill Dosanjh, promoter of the Super Boxing League, released the news in a statement and confirmed they were looking for a replacement to take on Khan.
Dosanjh said: "We are very sad to inform that our star Indian boxer Neeraj Goyat who was preparing for his mega-fight against Amir Khan met with a car accident last night that has caused him severe injuries on his head, face and left arm.
"He is currently in hospital and we wish him a speedy recovery.
“We are in the process of looking for Neeraj’s replacement. Please bear with us till we announce the new opponent of Amir Khan."
They wasted no time in finding a replacement, with the Saudis not wanting the promotion to be badly damaged due to their investment.
Australian boxer Dib confirmed he had agreed to take on the bout on Twitter just hours after the news of Goyat's injuries emerged.
Dib, 33, holds a 44-5 professional record and was formerly IBF featherweight world champion.
He challenged Tevin Farmer for the IBF super-featherweight crown in Sydney in his last outing last August, suffering a unanimous decision loss.
But he has vowed to take his "real life Rocky moment" against Khan next month.
He wrote: "In life you get a limited number of opportunities to do something monumental, and like the greatest in any industry will tell you, when an opportunity comes knocking you answer.
"This is my real life Rocky Moment."
His clash with Khan was set to be the biggest fight of his career so far, whilst Khan admitted this week he is desperate to get back into the ring to avenge his recent loss to Terence Crawford.
Asked about his Crawford defeat, Khan said: “That’s why I took this fight so quickly, I want to erase that memory.
“That fight, I just can’t live with it. It did upset me. I’m one of those guys who, if I get knocked down, I get back up. I fight with my heart.
“Reading the comments and stuff about me afterwards, that’s why I had to get this fight, to fight again as soon as possible.
"If that fight had not gone the way it did, I’d never have taken this fight. I want to erase that fight from my memory, move forward, get back to winning ways, and just keep busy.”
