OL players must operate as a synchronized unit. An individual OL player can have immense talent, but that doesn't necessarily translate to a very good OLine unit.
The Rams try very hard to keep the unit together as the cohesion of an OLine can only be gained from working together in practice and through the experience of many games.
The missing piece was at Center... we all knew that. It was desperation that caused the Rams to consider Corbett. It was a gift from heaven that Brian Allen emerged when he did. Now everyone is playing where they belong, and where they have previously played, and all is well in Ramland. I think that we are also deeper in subs than people might think as well. Keeping 10 OL guys on the roster was important so each could practice and learn primarily focusing on a certain position that best suits them (even though some cross training of course occurs).