Brian Melancon will replace Paulo Thiago and square off against TUF 17 champion Kelvin Gastelum at UFC Fight Night: Condit vs. Kampmann 2 on Aug. 28.
UFC Tonight's Ariel Helwani first reported the new opponent for Gastelum, and Gastelum confirmed the change on his Twitter. Gastelum hasn't fought since winning the TUF 17 title with a split-decision win over Uriah Hall on April 13.
Thiago was forced to withdraw from the fight with a knee injury.
Melancon won his UFC debut with a first-round knockout win of Seth Baczynski at UFC 162 on July 6.
The welterweight fight will appear on the main card of the event at the Bankers Life Fieldhouse in Indianapolis, Ind.