I'm less anxiety filled about Karras starting at C than I am about the back up situation. Clearly the jail breaks we saw last Thursday were the catalyst for today's moves. Karras is bigger, stronger, and more athletic than Andrews who had better technique, was quicker, and had more consistency than Karras had previously shown.
Karras has been in this system for 4 years now and I think the "can he make the OL calls" thing is overblown. It's not like he's a rookie. He's been asked to make OL calls for over 400 practices in his time with the Pats, so I think he knows them. Andrews had to do it as a rookie for 11 games and all but 2 the last 3 years. I'm confident that between the experience OG's and Karras we will get into the right protections a vast majority of the time. Eventually we might even see an improvement from Karras if he develops as most long term Dante' students do.
That being said, the back up situation is currently horrifying. Froholdt isn't ready (not that he should be), and Ferentz is having a bad summer. The health of our OL has been critical to the success of this extraordinary run. For the most part for the last 3 years our OL has pretty much been intact with only Cannon missing more than a couple of games over that time. It's a wonderful record, but the Pats would be fools not to believe that the pendulum might start swinging the other way eventually.
As of THIS moment, the "next man up" is pretty much non-existent. The new guys will need at least a few weeks to learn an entirely new system before they can be counted on to come in and play, whether they have any talent or not.
Right now, we'd better hope we have yet ANOTHER year of injury free luck from this OL because without it a strong strength of this team could quickly become a weakness. Because even if these new guys or any other OL pickups in the next few days are actually good acquisitions, our OL better be healthy for until the beginning of October at least. It will take at least that long to get any new guys up to speed.