Frederick's availability is by far the biggest factor. He not only handled the center position as far as the actual blocking, but made the protection calls. Looney filled in admirably, but Frederick is just better all around. And if Frederick is back and even 90% as good as before the illness, Looney is available to go to guard, if Williams is still weak at that spot, and since Williams was a tackle in college, he could fill in for either Smith or Collins....