They have thata big punishing RB on the roster right now and he's played well, but McVay doesn't want to use him. Is it because he doesn't block well in pass pro, isn't a threat to catch out of the backfield, can't learn the playbook, or what?

And what about Zack Evans? Why are we not seeing him?

It seems MvcVay wants a certain type of player at each position to fit his concept of what an offense should be. If the player doesn't fit the scheme or can't do the whole skillset at a journeyman level...