JuJu Smith-Schuster is playin' with fire!!!
The Pittsburgh Steelers rookie WR was asked to take a pic with a fan who happened to be wearing a Tom Brady jersey ... and he obliged.
BUT HE SNUCK IN A MIDDLE FINGER AIMED RIGHT AT #12!!
JuJu posted the pic on social media with the caption, "rt when you see it."
Yeah, we see it!!
It's funny -- gotta wonder if Mike Tomlin's laughing about it, too (hint: no).
BTW, JuJu lit up the Patriots when they played in Week 5 -- racking up 6 catches for 114 yards including a 69 yard crossing route that ALMOST won the game for the Steelers.