Lyoto Machida claims he was unaware the substance he took that led to his removal from Saturday’s UFC on FOX 19 fight with Dan Henderson was banned.

In a statement released on his Facebook page following the news Machida was out of the fight with Henderson after he had admitting to taking a banned substance, the former UFC champ explains he used a supplement called 7-Keto, which contains DHEA, a substance listed as an “anabolic agent” by the U.S. Anti-Doping Agency (USADA).

Machida (22-7 MMA, 14-7 UFC) claimed ignorance and said he didn’t know the substance was banned, which is why he revealed his usage of 7-Keto during a drug test prior to the scheduled rematch with Henderson (31-14 MMA, 8-8 UFC) at Amalie Arena in Tampa, Fla.

“Guys, I just wanted to let you know that I was caught off-guard, too,” Machida said in his native Portuguese. “It’s been very hard for me. I trained very hard for this fight. I dedicated myself a lot with my team. I want to tell you that I didn’t know about this substance. It was something that actually declared in my test. I said, ‘No, I’m taking all these things,’ and this substance was banned in 2016.”

Although Machida claims DHEA was banned as recently as this year, it’s listed as banned on the World Anti-Doping Agency’s World Anti-Doping Code as far back as 2005.

Machida, ranked No. 7 in the latest USA TODAY Sports/MMAjunkie MMA middleweight rankings, was set to return to the octagon for the first time since UFC Fight Night 70 in July, where he suffered a third-round knockout loss to Yoel Romero. Prior to that, Machida was submitted in the second round by current UFC champ Luke Rockhold.

“The Dragon” said he plans to accept full responsibility for his actions. His status as a first-time offender under USADA guidelines, which oversees the UFC drug testing policy and fighter sanctions, could mean up to a two-year suspension from competition.

“It was my mistake, and I own up to it because I didn’t know about it,” Machida said. “I just want to apologize to all of you, to all my fans, from all my heart. To all my team, to all my family. I always try to play fair, but this time, this happened.”

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