Gokhan Saki has been forced out of UFC 219, leaving Khalil Rountree to take on Michal Oleksiejczuk.
No reason was given by the promotion for the exit of Saki.
Rountree, a former Ultimate Fighter runner-up, has won back-to-back fights over Daniel Jolly and Paul Craig. Both victories came via finish in the first round.
Oleksiejczuk is unbeaten over the last two years, as the 22-year-old is 12-2 overall. Of his last nine wins, seven have been knockouts or TKO triumphs.
UFC 219 takes place December 30 from the T-Mobile Arena in Las Vegas and is headlined by Holly Holm challenging Cris Cyborg for the UFC female featherweight title.