Jake Paul says he's 100,000% positive his bro, Logan Paul, would wreck CM Punk in a real UFC fight -- and now he's firing back at Dana White, who's been trashing the idea all over town.
"Dana White's thinking small," Jake told us outside Craig's with his GF, Erika Costell.
Remember, after Logan fought KSI in a wildly successful pay-per-view fight on YouTube in August ... the social media star told us his goal is to fight in the UFC Octagon -- and he's dead serious.
Enter UFC honcho Dana White who immediately shot Logan down -- warning he'd get "hurt badly."
But, Jake says Logan's no punk bitch -- he's a real athlete with legit combat training.
"My brother's an athlete and has a wrestling background, 5th place at Ohio Division 1 state wrestling (in high school). Has boxed for a year now, will get another year of boxing under his belt before his next fight with KSI."
"Dana White, you might watch this, Dana. You're thinking small. I know you're about the money. Let my brother fight!!"
And, if CM Punk ain't down for the opportunity, we know someone else who wants in on the action.