Whether or not you're a fan of the personnel work that the Buffalo Bills and GM Buddy Nix have done over the last 16 months, it's tough to deny that they've done a ton of work to overhaul their defensive front seven.
When the Bills trimmed their roster to 53 players last September, they kept a total of 17 defensive linemen and linebackers on their final roster. Two of those players were gone by the end of the regular season. As it stands today (i.e. not counting current free agents), the Bills have 19 players in those positional groups. Four are players that Nix and the current regime inherited from Dick Jauron.
Kyle Williams isn't going anywhere any time soon. Chris Kelsay got a lucrative contract extension. Spencer Johnson has found a niche as a reserve, and Aaron Maybin... well, he's still here, too. Clearly, if the team brings back either Paul Posluszny, Keith Ellison or John McCargo as free agents, that number of incumbents would increase a tad.
Still, nearly 80% of the defensive front seven are imported players right now - including everyone from Marcell Dareus to Jammie Kirlew. There may still be work yet to do up front, but it's clear that the Bills wanted to change their personnel up front, and do it in a hurry.