Diaz has been out of the Octagon for six years but will return at UFC 266 for a rematch with old foe Robbie Lawler.
The duo first fought all the way back at UFC 47 in April 2004, with Diaz coming out on top.
Diaz's last fight was in 2015 and his last victory was in 2011, a decade ago.
Footage of 'Diablo' showing off his moves for a promotional piece has appeared online and many are unsure what to make of it
The 38-year-old is known for his endurance inside the cage and his slower movement is to be expected.
But many are still cautious over seeing the fan favourite make his return.
Am I seeing things or is he slow as hell there? Maybe it's a mind game.- Duncs (@DuncsMans) September 23, 2021
The only man I've ever seen lose shadow boxing https://t.co/qtKx2Tttu6- Adam Niland (@AdamNiland98) September 23, 2021
I worry for him ☹- Salty Jock Blogs:grinning: (@wobski421) September 23, 2021
Robbie went from -110 to -150 over night because of this video. I'm not even joking.- Uncle Drew (@tdrewcook) September 23, 2021
That one drunk uncle shadow boxing after watching the fights- Marlon Torres (@MarlonT6495) September 23, 2021
Despite the excitement for Diaz's clash with Lawler, the man himself has admitted he doesn't know why he's doing it.
He told ESPN: "I'm going in there to win. "Do I feel confident? I never do. I never have.
"I always feel like I'm going to get trashed out there. Every fight I've ever done.
"'How do you feel against Robbie Lawler?' I feel like I'm going to get the sh*t beat out of me. And even when I win, I get beat up worse."
Diaz then revealed that he'd much rather be facing UFC welterweight champion Kamaru Usman.
"I think I'll beat the sh*t out of Usman," the elder Diaz brother added.
"I'll have a better shot against Usman than I do Lawler, just because I already beat Lawler.
"This doesn't make sense for me to go in and fight Robbie Lawler again. I don't know why I'm doing this... This should not happen.
"Whoever set this up is an idiot. I don't know why I'm doing this. I don't know why this happened. I should be fighting Kamaru Usman - and that's it."
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