Back-up Center?

I was looking at the Lions' depth chart today I noticed that only one player is listed as a center, Raiola. Was wondering if anybody knows who the team plans on using as a back-up? I don't think any of the guards listed have any experience at center, so now what? Free Agency? I personally think Raiola is an average center at best, I have seen him get blown up by tackles over and over. Maybe the change to zone blocking will benefit him. At any rate, because I have to make this 75 words long, I was just wondering who else can play center that is on the roster currently?