Richard Towers has been forced to pull out of his showdown with David Allen at the weekend due to illness.
Towers was due to face Allen in a British heavyweight title eliminator on the undercard of Kell Brook's title defence in Sheffield on Saturday night.
American Jason Gavern has been drafted in as a late replacement to face Allen but the fight will no longer be a British title eliminator.
"I'm pleased Dave has a real fight on Saturday as he's really put himself through it in camp," promoter Eddie Hearn told Sky Sports News HQ.
"Gavern's CV is a who's who of elite talent and at this stage of Dave Allen's career, this is a real test"
Orlando-based Gavern is a veteran of 51 fights and returns to the UK following last year's clash with Anthony Joshua.
The 38-year-old was floored twice before being stopped by the Olympic champion in Newcastle 12 months ago.
Gavern has racked up 27 wins, 20 defeats and four draws since turning professional in 2003 and previously fought in the Prizefighter tournament when he lost to Reading's Michael Sprott in the final in 2013.
Allen also faced a late change of opponent in his last fight in October when he was due to face Adam Macaj in Sheffield.
Macaj was replaced by French heavyweight champion Fabrice Aurieng but Allen still managed to rack up his eighth straight win.
The 24-year-old, who is a good friend of Towers outside the ring, tweeted: "I don't know the issue with Richard although as his friend I hope everything is well with him, last I will mention his name now."