Heavyweight Matt Mitrione has replaced the injured Shane Carwin and will face Roy (Big Country) Nelson on Dec. 15.
Carwin and Nelson have been serving as rival coaches on Season 16 of "The Ultimate Fighter" and were due to fight in the main event of the televised UFC card in Las Vegas.
"WOW!! It never ends Carwin blew his knee out. Looking for a new opponent for Roy on the TUF Finale on FX," tweeted UFC president Dana White.
Nelson and Mitrione were both on coach Rashad Evans' team on Season 10 of the reality TV show.
Phil DeFries, originally scheduled to face Mitrione at UFC 155, will get a new opponent for the Dec. 29 card in Las Vegas.
In other UFC 155 news, Jim Miller is stepping in for an injured Gray (The Bully) Maynard against lightweight Joe Lauzon.