The OC hands down. Two reasons, f the OC can IMHO be competent this year then the Rams should score much more and keep the defense off the field and if he plays Bailey a lot more.
The others
Gurley, the Rams sacrificed high OL pick/picks to get this guy.
Then others Austin, agree on Fairley, Jenkins (stop making TD mistakes)
I would not say Foles because he has already shown he can be a very good QB.