In the modern NFL, assistants are hard to come by. Teams now need permission to move around for any 'lateral move', which includes coordinator jobs.
Which makes the trash heap the way to find guys. Coaches that are on fired staffs are the only ones you know you can get.
With five teams having fired staff, there's already some to choose from. And while assistants don't matter until there's a head coach, staff is a critical component to success.
Mike Solari - former architect of tough Kansas City OL, was a coordinator there for a year, and is a master of the WCO style running game. Fits with anyone, but has ties with Brian Schottenheimer through years with his father, Marty.
Tom Rathman - former fullback and 49er hero, is a fine WCO technician. More likely to stay than not, however.
Johnny Lynn - DBs coach that has coordinator experience, succeeding John Fox in New York. Entirely possible he coaches under Fox wherever he lands.
Eric Mangini - was a solid defensive coordinator. Players seem to rally around him but not consistent enough. Probably not a head coach by any means.
Brian Daboll - not an exceptional offensive coordinator, but has experience in the same system Carolina just finished up. Experience coaching QBs as well, and former Patriot coach.
Brad Seely - good ST coach, was here in 1995-98.
Rob Ryan - steely twin to Rex, no less crazy than his brother. Has some background in 4-3 but coached the 3-4 more recently. Very good defensive coordinator, potentially the best available that won't be a head coach.
Bryan Cox - former asshole linebacker in the NFL, now a solid defensive line coach. May follow Ryan and/or Mangini somewhat blindly.
Wade Phillips - he's a good DC. Fits with Brian Schottenheimer, having both been on staff in San Diego. A 3-4 only guy, with baggage. The rest of that staff likely stays.
Tennessee (projected staff change):
This is an "if" Fisher is fired.
Fisher is a head coach or nothing, so doesn't apply to this list. Getting any of these coaches means persuading the coach not to follow Fisher wherever he's going.
Dave McGinnis - former head coach of the Arizona Cardinals, assistant head coach. Excellent tactician and player's coach. Isn't a cooordinator, so might want one more shot at running a unit.
Geep Chryst, current Panthers TEs coach, was his offensive coordinator.