Former WBO super-featherweight champion Roman 'Rocky' Martinez will be replaced by Arash Usamanee on Saturday night for the bout against Raymundo Beltran.
Martinez has withdrawn through illness, according to Top Rank's Carl Moretti, who helps leading promoter Bob Arum with his co-operation.
With Manny Pacquiao taking on Timothy Bradley in the main-event, this was the Puerto Rican's chance to get back into title contention in front of a packed MGM Grand, which will be sold out.
Martinez (27-2-2, 16 KO) was set to move up to 135 pounds to face Beltran for the NABO title. After losing to unbeaten featherweight king Mikey Garcia in November, the 31-year-old was seeking another world title shot having not fought since that knockout defeat.
Beltran's new opponent Usmanee (20-1-1, 10 KO) has been out the ring for eight months, with his most recent outing ending in a draw against Argenis Mendez. Usmanee's only defeat came when he lost controversially to Rances Barthelemy in the 2013 ESPN Friday Night Fights season.
The 32-year-old Beltran is familiar to British fans as he was harshly robbed of the WBO featherweight crown last year. Coming to Scotland to fight Ricky Burns was always going to be difficult, but the Mexican scored a heavy knockdown and won the majority of the rounds to earn a decision according to most sat at ringside.
However, judges scored the contest a draw and a rematch was dismissed. Looking to get his career back on track, Beltran will be looking for a commanding victory to set up a potential world title shot at the end of the year.
Saturday's contest is scheduled for 12 rounds.
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