So the Rams now have a proven, experienced Center who has played at a high level. A back injury a couple of years ago seems to have hurt his play. I'll bet the signing took time because the medical staff needed time to evaluate the situation.
Backs can take a looong time to heal and restrengthen. I have experienced it and seen the same with others. It is just a very slow healing and rehabbing process. Since this is more than 2 years behind him, whatever it is now is probably about as good as it is going to get, at least with regards to playing football.
I still imagine the Rams will target a center in the draft, but now they don't need an immediate starter nor do they have to consider playing a rookie.
Brains and knowledge is half the battle for a Center.
So the Rams will now have an oline with 3 very experienced starters: Whitworth, Sullivan and Saffold. That itself ought to help significantly. And Sullivan already knows the system McVay will deploy (at least for the most part), so that is also a plus.
I suspect this is a one year situation. Two on the outside.