I don't think any one is saying it's super easy (atleast i'm not)but it isn't super hard either. Ricky Wagner was the top free agent right tackle once free agency started. Not only was he the best available but the free agent market at right tackle isn't really all that great and the same can be said about this year draft. His agent had every opportunity to make him the highest paid right tackle in the league and Wagner is clearly better than Lions former starting right tackle Riley Relief who was ranked 48 among right tackles.. Lions got the best right tackle available but if this draft class was better and there was more available quality tackles in free agency then I don't think Wagner get's nearly as much as he did.
Doesn't really matter where they line up because top pass rushers like Gerald Mccoy , Nadaukong Suh, Fletcher Cox, Calaisis Campbell, and more go up against centers all the time