Mirko ‘Cro Cop’ Filipovic abruptly announced at the start of the week that he was retiring from the sport, citing a shoulder injury as the reason, but it’s now emerged that there’s more to the story than that.

It’s now emerged that ‘Cro Cop’ appears to have been the first high-profile fighter to be caught out by the UFC’s new comprehensive drug testing initiative as USADA has just issued a suspension against the 41 year-old for a potential failed drug test.

“UFC announced today that a scheduled bout between Mirko Cro Cop and Anthony Hamilton in Seoul, South Korea has been canceled,” a statement from the promotion reads. “The U.S. Anti-Doping Agency (USADA) has notified both Mirko Cro Cop and UFC that he has been provisionally suspended at this time due to a potential Anti-Doping Policy violation.

“USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case involving Cro Cop. Additional information will be provided at the appropriate time in the process.”

Cro Cop may have hinted at the issue in his retirement statement on Monday when he noted that he had used, “injections of blood plasma and various cocktails of drugs” while trying to heal his shoulder injury in time to compete at UFC Fight Night 79 later this month.

The Croatian fighter returned to the UFC back in May where he avenged an old loss to Gabriel Gonzaga, winning by TKO in a ‘Fight Of The Night’ performance.