Diaz takes on Anthony Pettis at UFC 241 in Anaheim, California, this Saturday.
The ‘Stockton Slapper’ is competing in the octagon for the first time since his defeat to Conor McGregor in 2016.
After that fight, Diaz landed himself in hot water by smoking a cannabis oil cigarette in his post-fight press conference.
And it appears he’s done it again ahead of his comeback.
Diaz lit a similar cigarette when participating in his public workout, before passing it out into the crowd.
According to Marc Raymond of ESPN, the joint was CBD from hi own brand at Game Up Nutrition.
The substance is entirely legal for fighters to take, and does not violate any anti-drug regulations.
UFC president Dana White didn’t seem too happy, however.
The promoter tweeted a video of the star with the emoji of someone covering their eyes.
Many UFC fans feared that Diaz wouldn’t fight again after suffering defeat to McGregor at UFC 202, a fight the American still believes he won.
And Diaz admitted he was close to calling it a day, and suggested he should have quit after beating McGregor in their first fight at UFC 196.
“I should have beaten his a** and been on my way, but I have morals and said let’s do it again then,” he told ESPN.
“Some people don’t have that and that’s why they’re not real fighters.
“[If I was McGregor], I wouldn’t be able to sleep at night; he got smashed in his face and choked in front of everyone.
“He got his rematch like a spoiled little baby then came back and won a little decision that could have gone either way.
“I don’t even care if it’s a big decision, it’s not the same; you can’t be content with a decision, you got choked on your face.
“Time will tell but I think we will fight again.”