I think the Bills lose out on both Brown and Birk.
Dont be surprised though if one of the "first day signings" tomorrow end up being Brad Meester or Jake Grove, one of the second tier Centers on the market. The sign a veteran FA, draft a Center and let them battle it out in camp. My money is on Brad Meester, he's got a lot of starting experience under his belt and is used to playing in a run-first offense.
Also, the Bills will sign Brandon Moore, methinks.