My best guess is that Smith, Parnell, Livings, Costa, and Berny are locks for the roster. If you made me hazard a guess I think Bernie will be the starter at center and Costa will be his backup. If Killa comes on strong and can make a push at center/guard then you have 3 guys that can play at center.
I think this is the Cowboys thought process and we are keeping Free as a smoke screen to cover up our interest at right tackle hoping one will fall to us at 18 and that someone right below us won't leap frog us and get him. At least that is my hope. If we draft a right tackle in round one you can say goodbye to Free immediately after the draft and he will probably be cut immediately after the the draft anyway because he will be useless as a smoke screen after the draft.