Mark Geragos says he knows "beyond a shadow of a doubt" the NFL blackballed his client Colin Kaepernick ... and it's entirely because of Donald Trump.
Kaep's attorney -- who's reppin' the former QB in his collusion case against the league -- revealed some of the ammo he's usin' to prove his case on Amy Dash's podcast Tuesday ... and he says it all starts and ends with Trump's disdain for anthem protests.
"[We] got an owner under penalty of perjury testifying that he changed his mind after he was told what Trump said," Geragos said.
The league's new anthem policy ... the blackballing of Kaep ... the unwillingness to sign fellow anthem kneeler Eric Reid -- Geragos says it all stems from POTUS.
"The only reason -- and the owners will admit that -- they haven't signed [Kaepernick] is they're afraid of Trump, and they've colluded because of Trump."
Geragos added: "Basically, at this point, they've made the choice that they're going to opt on the side of the white, nationalistic side, as opposed to any other demographic."