James Harrison says it ain't just Big Ben and the Steelers' D causing problems in Pittsburgh ... 'cause the legendary LB tells TMZ Sports it's time start pointing fingers at Mike Tomlin as well.
"I think now, a lot of it has to be put on to what the game plan is -- the coaching."
Tomlin's been Teflon in Pitt -- the dude does have a Super Bowl ring -- but a lot of people ... including Terry Bradshaw himself ... have grown tired of seein' him as head man.
Doesn't seem James is quite at that point yet -- but the ex-Steeler does tell us the coaching DEFINITELY needs to improve if Pittsburgh wants to end its 3-game losing skid.
"Now it's actually where you gotta kick it in -- and EVERYBODY has to be held accountable. From the top down."
Tomlin and the staff better get going quickly ... the Steelers have Tom Brady and Bill Belichick this week.