It is actually funny.
There is so much "trust in the talent evaluation of our staff" mantra for every single player unless your name is Turbin. Obviously the staff must see something in Turbin since they not only kept him around, they kept him when they had a surplus of backs.
So let's go over a few issues.
Turbin is only in his second year. He is going to get better. He already has a great tendency to rocket into the hole (whether the hole is there or not) and he runs with a fair amount of power considering his running style. He is a great back to have for both short yardage AND for receiving (though I believe he missed a few important passes last year in the playoffs, he has looked solid this year catching the ball).
Turbin runs with far, far too much lean. That means his center of gravity is so far forward it is harder for him to change direction and it also means he has a tendency to fall forward when tackled low. This is a curse and a blessing. It means he gets tripped up by nearly anything as he is already nearly falling as he runs, but it also means that he is generally not going to get a loss because he is going to fall forward.
Also Turbin runs with his legs too close together, it is good for speed but bad for power. The fact he gets as much power as he does is probably a good sign.
Since the tendency to lean forward and not keep a wide stance can be trained/conditioned out of him, he might become a pretty good back. He will never be elusive like a Forsett but he certainly can run it up the gut and break the occasional longer run even if he is eventually caught.
I think it is not unreasonable to consider him a very raw RB that can become an average to slightly above average power back. That is useful.
Additionally, his receiving skills are already decent - there is no reason he could not become a poor man's J L Williams type without the FB blocking skills.