"Brady might as well retire!!!"
That's Tennessee Titans legend Chris Johnson gloating his face off after his squad beat the Patriots ... with CJ2K advising TB12 to hang it up for good!
Johnson -- who spent 6 seasons with the Titans back in the day -- was a VIP guest with the team at Gillette Stadium on Saturday night. And when the team came out with the "W" in the Wild Card round, Chris got right in the middle of the action!
"I told you we was gonna smack this sh*t man," Johnson shouted after the 20 to 13 victory .