Diaz is a veteran of MMA with 34 bouts but at the age of 38 he is making his professional boxing debut against Jake Paul.
And ahead of the August 5 bout, the American denied suffering from chronic traumatic encephalopathy.
Diaz said on The Pat McAfee Show: “These f****** are talking about how I talk, and I’ve got f****** CTE or some s***.
“I’m like, ‘Bro, I’ve been talking this way the whole motherf****** time.’ It’s got nothing to do with getting hit or none of that.
“I’m smarter now than ever.”
CTE is a progressive and fatal brain disease associated with repeated head trauma, including concussions and repeated blows.
It is also associated with the development of dementia and has affected fighters and NFL stars.
Diaz – who has suffered nasty cuts to the face during his career – is looking to maintain his record of having never been knocked out.
He said: “I don’t really be eating punches like they say.
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“I bleed because of the forearms and elbows and s*** cut me up but like I said, I’ve been in a boxing gym and it might not look like it but I roll with a lot of these punches that anybody lands on me.
“I’m not just walking in like a meathead into punches. I’ve never been knocked out. I’ve never even really been f****** stunned stupid or nothing.”
Paul, 26, returns off the back of his first ever defeat, losing a split-decision to Tommy Fury, 24, in Saudi Arabia.
And he will do so in his first-ever fight scheduled over ten rounds.
Paul said: “I’m going to make sure it’s a living hell the whole time.
“I think that he’s got a long night ahead of him. I do as well but I’m not afraid of it. I’m ready to rock and roll.”
