Found an older SI article about the Top 10 players who likely to go undrafted, they call it the Welker Watch List (because he was undrafted). As it turns out, the Bills ended up with 3 out of 10 players on the list (David Nelson, Danny Batten, and Levi Brown). It gives me a little confidence that the Bills are adding the most important players to their roster, not the big free agents or 1st day picks... but the players that seem to show up out of nowhere to become producers. If they are successful in the back end of their drafts then all of a sudden your roster becomes deep, robust, and gains longevity. For as mediocre as Gailey's W-L record is in the NFL, he never really was given any extensive amount of time to craft a roster. 

http://sportsillustrated.cnn.com/2010/writers/don_banks/04/02/list/index.html