James Harrison spent the majority of his career playing under Mike Tomlin, who isn’t all that much other than he currently is. The Pittsburgh Steelers’ all-time sack leader didn’t even get a chance to be a full-time starter until Tomlin’s first season with the team in 2007.
It’s hard to say how much of his opinion is tainted by the manner in which things ended between them, but Harrison hasn’t been shy about his criticism of his former coach since he retired—actually since he was released, since he even said things at that time.