You don't know football if you think Kirk Cousins ain't worth his $84 MILLION deal ... so says his teammate Laquon Treadwell who tells TMZ Sports the QB is "a baller."
Of course, Cousins had a pretty rough first season in Minnesota after inking a mega-contract ... losing a must-win game to the Bears that kept the Vikes outta the playoffs.
But, 23-year-old Treadwell -- the Vikes' 1st-round pick in the 2016 Draft -- says just because the first season didn't go according to plan doesn't mean the QB wasn't worth the money Minnesota paid him.
"That's a lie, man," Treadwell told us when we got him out at LAX this week ... "He a baller."
Cousins did throw for 4,298 yards and 30 TDs ... and Treadwell had his best season yet with the new QB -- and he tells us better years are coming.
"It's the first year. We was a little rusty, but we're going to bounce back. You know? We was learning each other. Chemistry."
We also asked Laquon about the upcoming NFC and AFC Championship Games -- and while he wouldn't mind seeing a Brees vs. Brady Super Bowl ... it sure sounds like he wants a Rams-Chiefs big game!!!