The UFC announced Thursday it was made aware the U.S. Anti-Doping Agency (USADA)—which serves as the independent administrator for the sport's anti-doping policy—told Nick Diaz of a possible violation.
The violation comes "from Diaz's alleged accumulation of three Whereabouts Failures within a 12-month period," the announcement read.
As a result, Diaz was provisionally suspended pending the situation's eventual resolution.
Diaz hasn't fought since January 2015 when he lost a decision to Anderson Silva.
However, John Morgan and Ken Hathaway of MMAjunkie noted the result didn't stand because Silva tested positive for performance-enhancing drugs and Diaz tested positive for marijuana metabolites.
Diaz's last win came all the way back in 2011, and UFC President Dana White recently said he doesn't think the 33-year-old will ever fight.
"I just don't think he has the desire anymore," White explained, per Morgan and Hathaway.