Chris Weidman knows it's do-or-die time when he fights Kelvin Gastelum this weekend ... and told us he's gonna shut up all the haters who say he's washed up.
Weidman's had a rough go as of late -- going from undefeated champion to losing his last 3 fights -- and some people are questioning whether he's still got it.
Chris told TMZ Sports those haters are in for a violent awakening ... 'cause he's about to put a hurtin' on Gastelum -- and prove the champ is BACK.
Weidman's so locked in, he even took shot at all the 185-pounders before signing off.