Carl Frampton will now face Canadian Steve Molitor in Belfast on Saturday 22 September after European super bantamweight champion Kiko Martinez withdrew from the fight through injury.
Two-time world champion Molitor will challenge Belfast boxer Frampton for his Commonwealth and IBF International titles at the Odyssey Arena.
"This is a much tougher fight for Carl," said his manager Barry McGuigan.
"But it's the kind of fight we want him to be in," added the ex-world champion.
The news of the Spaniard's withdrawal led to a search for a new opponent, which culminated in the announcement that the classy Molitor would be coming to Belfast.
Steve Molitor will replace Martinez as Frampton's opponent
A statement from promoters Matchroom Sport did not specify the nature of Martinez's injury.
Molitor first held the IBF belt in 2006 after beating Michael Hunter in the UK and successfully defended it five times before regaining it in 2010.
The 32-year-old has fought four times in the UK, with wins over Hunter, John Mackay, Nicky Booth and Jason Booth and he has promised an explosive night when he crosses the Atlantic to lock horns with Frampton.
"I love fighting across the pond," said Molitor. "I've won four from four over there and plan on retaining that perfect record.
"I am excited about fighting Frampton - although he is not a household name amongst the rest in my division, he is recognised as a future star.
"Although I am coming in off of Martinez stepping out, I have been training like a mad man for several months - I am not hungry, I am starving.
"Eddie Hearn (promoter), Barry McGuigan and Frampton, you have all the respect in the world from me - stepping up against me, as a two-time IBF champion of the world, takes courage."