I haven't seen it mentioned, but I think there's a chance this has nothing to do with a lingering injury or contract extension this year. JT is a traditional RB that needs an old school system to maximize his impact and therefore his value to a prospective franchise. I think there's a chance his current "holdout" is an effort to be traded to a run heavy team because he knows he doesn't fit into the Steichen system. To get as many snaps as he has to this point, he will need to prove himself capable as a runner, pass-catcher, and blocker. I can see JT believing that this confrontation with the front office is less costly than playing his last year before an extension with the expectation that he fills all of those roles effectively.