Sean McDermott (former CAR DC) is the new HC in Buffalo. He's brought in Leslie Frazier (former BAL DB coach but also MIN HC) as the DC. Odds are, they are switching from a 3-4 to a 4-3. This means Jerry Hughes, Lorenzo Alexander and Shaq Lawson could all go from LBs to DEs. The real question will be at LB. Preston Brown, Zach Brown and Reggie Ragland could all be vying for two useful spots. Preston had a good year after a rough 2015. Zach had a huge year in place of Ragland, but he's a UFA so it'll be interesting to see if they bring him back. Ragland should be back to full strength by the start of the season.
Wade Phillips (former DEN DC) signed on in LA. If they switch to a 3-4, like Denver ran, it could have some major ramifications. Aaron Donald could become a DE in a 3-4. He should still be highly productive, but it remains to be seen if he has the same level of value as he did as DT1. Robert Quinn would be the other big change here if he moves from DE to LB. Odds are, Alec Ogletree and Mark Barron will be the two ILBs as LA doesn't have any other notable LBs on the roster.
Joe Woods (former DEN DB coach) will take over as the Denver DC. Vance Joseph (former MIA DC) was hired as head coach. Joseph ran a 4-3 in Miami but would anyone really try and change that defense? Joseph also got Woods the Denver DB's coach job under Kubiak.
Matt Burke (former MIA LB coach) will be the new Miami DC so I wouldn't expect much change there.
Jacksonville is retaining Todd Wash as their DC even though they fired Gus Bradley. Not much should change here.
Washington is struggling to find their new DC. They've interviewed Mike Pettine (former CLE HC and BUF DC), Gus Bradley (former JAX HC and SEA DC), Rob Ryan (former BUF assistant and NO DC) and Greg Manusky (WAS OLB coach). Bradley should be their top choice but the position isn't the most coveted in the league. Most likely, they're sticking to a 3-4, especially if they go with Manusky. If they do move to a 4-3, some definite value would be generated. Ryan Kerrigan, Preston Smith and Trent Murphy could all become DEs. Murphy is a solid known commodity but Smith has a ton of potential. He led rookies in sacks in 2015 with 8, 2 more than Danielle Hunter.
The Chargers are still looking for their DC as well. They've also interviewed Gus Bradley, but that's still up in the air (see below). If Bradley or another DC switch LAC over to a 4-3, it might make Joey Bosa safer. He played a lot of snaps with his hand up this year. It's a slightly risky situation if the Chargers stay in 3-4. Melvin Ingram is a UFA but if he resigns and switches to a DE, he would be very valuable. Their ILB situation was starting to shake itself out at the end of last year as Jatavis Brown was getting healthy, but it wouldn't be hard to imagine Brown as their Will and Denzel Perryman as their Mike.
San Francisco is still looking for their entire coaching staff. The front runner for HC is Kyle Shanahan (Atlanta's OC). They have to wait until Atlanta is done for the season though. Josh McDaniels has made a good decision and decided to remain as the NE OC because SF has almost no talent and has fired 3 coaches in the last 3 years. They're also looking at Tom Cable (SEA O-line coach). I read that Gus Bradley is waiting until this decision is made because he'd prefer to work with his former colleague Cable. Bradley is the best DC candidate remaining so once SF picks a head coach, all the remaining cards should hopefully fall pretty quickly. The ramifications of Bradley or another DC switching SF to a 4-3 are hard to imagine. They've spent their last two 1st round draft picks on Arik Armstead and DeForest Buckner, two 3-4 DEs. Conventional wisdom assumes they'd both slide inside and some combination of Aaron Lynch, Ahmad Brooks, Eli Harold and some draft picks in a deep Edge class would be the DEs. Navarro Bowman is the only ILB who played this year who's still under contract for next year, so even if they stay a 3-4, watch what they do in the draft this year. If they do switch to a 4-3, watch who resigns or gets drafted to potentially be the Will next year.