Agree with steveishere & DarkaneRules
Linsley is the guy. He was drafted specifically for this purpose.
If Tretter gets IR'd (for return or otherwise), I'd expect Gerhard to get promoted to backup.
If Tretter is not IR'd, then we go with 7 OL and if Linsley is hurt mid-game, we move Lang to C and cross our fingers.
For Linsley, he'll have an All Pro guard to his left and a legit Pro Bowl caliber guard to his right.
Lang & Sitton are as good of a guard tandem in the league when healthy, should make playing center easier.
I am chosen by many but taken by no one.