This sounds like a hypothetical question to me?
I'd be surprised to see Sirles at Center. Typically guard types are more suited to move to center than tackle types. I also think Sirles is a bit stiff in the upper body to play center. He would be okay pulling but I think there are others that are more nimble to manuever inside. He has good experience at tackle and can lend leadership there. He has played both sides so that helps depth. Tackle doesn't have a lot of depth or experience. I think Brandon Thompson might be more of an option at center than Sirles.
Moore,Sirles,Sterup
Choi,Reeves,Klatcho
Pensick,Jackson,Pelini,Price
Long,Thompson,Cotton,Moudy
Sirles or Arod, Qvale