Dereck Chisora will face David Price on 26 October in a British heavyweight bout where both men will risk their careers, says promoter Eddie Hearn.
Chisora, 35, was set to face Joseph Parker until the former world champion withdrew following an illness he believes stemmed from a spider bite.
Price, 36, has stepped in and enters the bout off a run of three victories.
"I kept in the gym all summer as I had a feeling I had to be ready for a call like this, and ready I am," Price said.
The bout, at London's O2 Arena, will form part of the undercard to the world title fight between super-lightweights Josh Taylor and Regis Prograis, which is the final of the World Boxing Super Series.
Chisora has previously expressed his displeasure at not being the night's main event and threatened to walk away from competing if he was not paid more.
But following news of Liverpool's Price taking part he said: "David Price has stepped up and I'm ready for whatever he brings. This is north versus south and in my home town I write the rules."
Price - who has 25 wins from 31 outings - and Chisora - with 31 wins from 40 contests - have both built momentum in recent fights with strong displays.
But with each vying to push forward from the elite level domestically to become part of the conversation among the very top heavyweights globally, a defeat for either would prove damaging at such a late stage in their careers.
"It was frustrating to lose the Parker fight but I feel we now have a fight with even more curiosity and danger," said promoter Hearn. "The careers of both men are on the line, they will be giving it everything. It's going to be a dramatic fight and dramatic night."