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 ... "I already knew it!"

"We told 'em we was gonna get that sh*t!!!"

The bragging and the smack talk continued outside the locker room ...

"Brady might as well retire! We done painted that sh*t!"

Watch the video, Johnson is convinced we've all seen the last of Brady on the Patriots -- and maybe forever!

For his part, 42-year-old Brady didn't sound ready to retire in his post-game press conference ... telling reporters it's "hopefully unlikely" he quits pro football for good.

"I love the Patriots. It's the greatest organization," Brady said.

"Playing for Mr. [Robert] Kraft all these years, and for Coach Belichick, there's nobody who's had a better career, I would say, than me -- just being with them. So, I'm very blessed."