Caraway was forced to leave the card with an injury, and now Martins is out with an injury as well. Sterling, who replaced Caraway in the first place, now takes on fellow UFC newcomer Gibson on Feb. 22.
Sterling enters the Octagon with a perfect 8-0 record with five finishes, including wins over Bellator fighters Claudio Ledesma and Sergio da Silva, and a submission victory over WSOF veteran Sidemar Honorio.
Gibson (11-3) makes his UFC debut riding a six-fight win streak with four stoppages. Gibson, who lost to UFC veteran Ulysses Gomez in a title fight at Tachi Palace Fights in 2011, is 5-0 since returning to the bantamweight division.
UFC 170 takes place at the Mandalay Bay Events Center in Las Vegas, Nev., and is headlined by Ronda Rousey vs. Sara McMann for the women's bantamweight championship.