Mirko Cro Cop caught wind of recent comments in which Roy Nelson said Cro Cop would be on “special supplements” for their Bellator 200 rematch.

Cro Cop clearly isn’t happy.

After their rematch was recently announced for May’s Bellator 200 event, Nelson (23-15 MMA, 1-1 BMMA) spoke to MMAjunkie and said the possibility of a lack of stringent drug testing for the fight could potentially allow Cro Cop (36-11-2 MMA, 0-0 BMMA) to fight while doped.

Cro Cop is riding an eight-fight winning streak, which is the longest of his storied MMA career. Most of those wins took place under the Rizin FF banner in Japan, where drug testing is notoriously almost nonexistent.

Other than a 2015 issue with the U.S. Anti-Doping Agency (USADA), Cro Cop has no formal drug-testing issues. That didn’t stop Nelson from speaking out, nor did it prevent Cro Crop from firing back at Nelson’s “fat disrespectful ass” with some harsh words of his own (via Facebook):

“Dear Roy Nelson,you dont have to worry that i’m using any ‘special supplements’ as you claim.the only ‘special supplements’ i’m using is 2 hard and bloody trainings per day,five days a week.and i will be tested,like all others, during preparations for the fight and before and right after the fight.so you can be calm.and start thinking of some good excuse after i beat up your fat disrespectful ass,you have enough time to may 25.and do me a favour please,and shave that disgusting beard, look like professional fighter and show respect to your opponent.good luck!”

Bellator 200 takes place May 25 at The SSE Arena in London, and the main card airs on Paramount via same-day delay.

Cro Cop vs. Nelson marks a rematch of a bout from UFC 137 in October 2011. “Big Country” stopped Cro Cop by third-round TKO at the event, which sent the Croatian into one of his many short-lived MMA retirements.

Nelson is coming off a majority-decision loss to Matt Mitrione this past month at Bellator 194, which eliminated him from the yearlong Bellator heavyweight grand prix. Nelson, though, said he hopes spoiling Cro Cop’s Bellator debut will allow him to rejoin the tournament field as an alternate later this year.

For more on Bellator 200, check out the MMA Rumors section of the site.