Diego Sanchez has pulled out of his fight against Donald Cerrone for undisclosed reasons, sources told MMA Fighting's Damon Martin and Steven Marrocco.
The welterweight contest was scheduled to serve as the co-main event of UFC Fight Night on May 8.
A replacement is reportedly being sought to face Cerrone next week.
Sanchez was looking to rebound from a loss to Jake Matthews last September. "The Ultimate Fighter 1" winner is 1-2 in his past three outings, including a disqualification victory over Michel Pereira.
"Cowboy" is riding a five-fight winless streak, with his last bout against Niko Price ending in a majority draw. The 38-year-old hasn't been victorious since he met Al Iaquinta in May 2019.
UFC Fight Night doesn't currently have a main event. The card was supposed to be headlined by TJ Dillashaw's return against Cory Sandhagen, but the former bantamweight champion pulled out Tuesday after suffering an injury in training.