I don't know. He's been very upfront about his reasons, and I think blackballing him for it is pretty extreme.

http://www.sbnation.com/2016/9/11/12...n-marshall-nfl

I have great respect for the men and women that have fought for this country. I have family, I have friends that have gone and fought for this country. And they fight for freedom, they fight for the people, they fight for liberty and justice, for everyone. That’s not happening.
I could see guys like Greg Hardy, Ray Rice, or AP not getting signed, and Vick getting back in the league had me gobsmacked. Protesting like this -- and others joined him, mind you -- isn't illegal. The concept of "blackballing" makes me instantly think of ol' Sen. McCarthy by the way.


That part of it aside, he has enough talent to at least be a backup or spot starter for a game or two. I don't know how invested he is in the game; I think he's more interested in social justice than football, and if your QB is your leader he has to be 100% committed.
He would also need a lot of QB development -- he's not done learning the position at the pro level, and may never learn it. He may not want to be a backup either...some guys still think they can/should be the starter. You'd think losing out to Blaine Gabbert would have changed that, however.