Matt Barnes Punks Instagram Troll ... 'Say It To My Face'

Matt Barnes lost his patience with an Instagram troll Wednesday morning -- and issued the guy a crazy challenge, "You wanna talk sh*t say it to my face when you see me."

The NBA star was pissed off over a guy who was trashing him in the comments section of a pic Matt had posted earlier in the day.

But instead of letting trolls be trolls, Barnes decided to lash out with a message of his own ... captured by our friends at BSO.

"But seein you wanna talk sh*t say it to my face when you see me. Everyone is mike Tyson on social media."

Questionable move from a guy who was being investigated for getting into a REAL LIFE fight with another NBA employee recently ... but it's clear, Matt doesn't care.