Perennial featherweight contender Chad Mendes has been flagged for potentially violating United States Anti-Doping Agency policy. The violation is stemming from an out of competition testing done by the USADA.

Mendes (17-4) has long been considered the best featherweight in the world not named Jose Aldo. He has twice fought for the UFC’s featherweight title and has twice lost to Aldo. He famously step in as a last-minute replacement to face Conor McGregor at UFC 189. Mendes would then go on to lose to Frankie Edgar in December of 2015. Mendes has not been scheduled for a fight since the loss to Edgar but under USADA policy all fighters are subject to year-round drug tests.

The UFC have already issued a statement on the news of Mendes’ potential violation:

“The UFC organization was notified today that the U.S. Anti-Doping Agency (USADA) has informed Chad Mendes of a potential Anti-Doping Policy violation stemming from an out-of-competition sample collection.”

“USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case. It is important to note that, under the UFC Anti-Doping Policy, there is a full and fair review process that is afforded to all athletes before any sanctions are imposed. Additional information will be provided at the appropriate time as the process moves forward.”

Mendes now joins the likes of Lyoto Machida, Yoel Romero, Frank Mir, and BJ Penn as fighters who have been flagged for USADA violations in the past several months.