Briton Lone’er Kavanagh has stepped in at less than a month’s notice to fight Brandon Moreno in Mexico on 28 February.
Earlier this week Asu Almabayev withdrew from the flyweight contest with Moreno because of injury.
Kavanagh, 26, had been booked to fight at UFC London on 20 March and will now face by far his toughest test to date against the former flyweight champion.
The Mexican will have the weight of a famously feverish home support behind him, but is at a crossroads in his career with three defeats in his past five appearances.
Moreno, 32, was stopped by Tatsuro Taira in his last outing in December but remains ranked at number four in the division.
Kavanagh, ranked 15th, can boost his status considerably with a win on away soil.
The Londoner suffered the first defeat of his MMA career in his last bout in August, losing by stoppage to Charles Johnson.
Though Kavanagh is now off the UFC London card, there will still be plenty of British fighters in action.
Featherweight Lerone Murphy headlines against Movsar Evloev, while Nathaniel Wood, Luke Riley, Michael ‘Venom’ Page, Christian Leroy Duncan and more are set to appear.