Dmitriy Salita overcame third-choice opponent Brandon Hoskins at the Barclay Center in Brooklyn to take another step towards a second world-title challenge.
Hoskins, from Missouri, gave Salita a useful test over six rounds before the Jewish welterweight prevailed by scores of 60-54 and 59-55 twice.
Hoskins, beaten for only the third time in 20 fights, was brought in at short notice.
Original opponent Vivian Harris was forced to withdraw following his recent knockout by British champion Brian Rose in Blackpool.
Hector Munoz, from Albuquerque, New Mexico, was then pencilled in but that match-up also failed to materialise.
The Saturday night fight meant Ukraine-born Salita, an orthodox Jew, had only 40 minutes from the end of Shabbat until fight time so he stayed in a nearby hotel, walked to the arena and gloved up.
Perhaps understandably, he took time to get into his stride against the aggressive Hoskins before taking control in the second half of the fight and having a particularly good fifth round.
The victory took his record to 35 wins and one draw from 37 fights, with his only loss coming in a WBA world light-welterweight title fight against then champion Amir Khan in Newcastle four years ago.
Salita, 30, now hopes to challenge fellow Brooklyn resident Paul Malignaggi who climbed off the floor in the 11th round to retain his WBA welterweight title with a majority decision over Mexico’s Pablo Cesar Cano on the same bill.