Uriah Hall knocked out Adam Cella with a nasty spinning heel kick to the head in the episode of "The Ultimate Fighter" that aired Tuesday.
There was little celebration, however, as Hall and the other fighters waited anxiously for Cella to recover as doctors worked on him after the late first-round knockout.
"One of the nastiest knockouts I've ever seen in the fight business, let alone on 'The Ultimate Fighter,'" said UFC president Dana White. "It's one of those one you want to celebrate, but you don't."
UFC co-owner Lorenzo Fertitta had teased the episode by tweeting it as "one of the best episodes in series history!"
Cella was pronounced OK, pending a trip to hospital for a CAT scan, reported referee Steve Mazzagatti.
"He's conscious. His memory will come back within the next hour or so," Mazzagatti said.
It was the second win in as many middleweight fights for coach Chael Sonnen's team over Jon Jones' following Luke Barnatt's KO of Gilbert Smith.
Sonnen then selected Kevin Casey to fight Collin Hart of Team Jones.