The Buffalo Bills are officially switching back to a base 4-3 defense, so it's time to briefly re-assess the team's personnel in the front seven. To generalize before we get into specifics: it's looking like five of the front seven positions are already locked down.
Mike position settled: The one position that Chan Gailey addressed specifically on Monday was middle linebacker, where Gailey confirmed that Kelvin Sheppard would be next year's starter. This is not surprising; the team has long been high on the second-year player.
Playing Sheppard inside frees up veteran Nick Barnett to keep playing on the weak side of the alignment, where he put together a Pro Bowl-worthy stat line for the Bills in 2011. Barnett will also remain the team's every-down linebacker, staying on the field in passing situations, and will also likely be the team's go-to blitzer from the linebacker position.
Strong-side 'backer needed: The one position at linebacker in need of an upgrade is the strong-side linebacker position. This player aligns on the strong side of the formation (obviously), and therefore needs a bit more girth to take on extra blockers, but also cannot be a huge liability in coverage. This player will not be an every-down player - he'll be the first linebacker off the field in nickel packages - so it shouldn't require gobs of money or a premium draft pick to fill it.
The Bills have a lot of options at this position from their current personnel, which is more indicative of their lack of a good option than anything else. Chris White might be the closest athletic fit to fitting the position currently, though he's more of a middle linebacker, and I think Arthur Moats may get a look there, specifically for his pass-rushing abilities. Neither is a great fit, however, so the Bills should look to upgrade.
Defensive End: Chris Kelsay is the third of the five locks for a starting job, joining Sheppard and Barnett. He'll play defensive end, and in all likelihood will be an every-down defender from that position. As you all are well aware by now, the team desperately needs a premium pass-rusher, and therefore, there's one end position that's up for grabs.
Shawne Merriman is no longer suited to be an every-down player in this league, so attempts to pencil him into the starting lineup at right end are ill-conceived, in my opinion. His role should be limited - perhaps severely so - to keep him healthy and maximize his effectiveness, if he's even around at all. Right now, the best-looking option at end aside from Kelsay, to me, is Kyle Moore. Yeah... the Bills need help here very, very badly.
Defensive Tackle: Kyle Williams and Marcell Dareus will start, and they'll serve as the foundation for everything that the Bills do defensively. This much is obvious.
The team has a ton of depth options, including wide-bodies that will play reserve run-down roles (Torell Troup and Kellen Heard), and smaller, quicker guys that can slide inside and rush on passing downs occasionally (Spencer Johnson, Dwan Edwards and Alex Carrington). But Williams and Dareus should be as close to every-down players as is feasible at a position where staying fresh is highly important.
When it's all said and done, I've got a loose starting lineup that looks like this:
LE: Chris Kelsay
DT: Marcell Dareus
DT: Kyle Williams
MLB: Kelvin Sheppard
WLB: Nick Barnett
Fundamentally, the team's needs have not changed, however. They're still much stronger up the middle than they are on the edges. The pass-rushing need transitions from needing a stand-up rusher to needing a rusher that can play with a hand in the dirt. They still need players that can set the edge against the run, and they still need more overall speed in their front seven, though that need has now increased at linebacker.