Dabo and Saban played DB, but I think Saban is the exception. He just has it. Plus I would say those three are outliers.
Nick Saban - DB as a player, DBs Coach and LBs Coach
Urban Meyer - DB as a player, QBs, WRs, DBs and OLBs Coach
Dabo Swinney - WR as a player, WRs Coach
Bill Belichick - Special Teams Coach, WRs Coach and LBs Coach
Bobby Bowden - QB as a player, WRs Coach
Bill Walsh - RBs, DBs, WRs Coach
Eddie Robinson - QB as a player
Don Shula - DB as a player, DBs Coach
Paul Brown - QB as a player
Joe Paterno - QB, CB as a player
Bud Wilkinson - QB as a player
Tom Osborne - QB, WR as a player
Bob Stoops - DB as a player, DBs Coach
Steve Spurrier - QB as a player, QBs and WRs Coach
Tom Landry - CB, Punter, QB, RB as a player
Bill Parcells - LB as a player, LB Coach
Pete Carroll - QB, WR, DB as a player, DBs Coach
Mike Tomlin - WR as a player, WRs and DBs Coach
Bill Cowher - LB as a player, Special Teams and DBs Coach
Tom Coughlin - RB as a player, QBs and WRs Coach
Tony Dungy - QB and DB as a player, DBs Coach
Dennis Green - RB as a player, RBs, WRs and Special Teams Coach
Don James - QB as a player (at The U), DBs Coach
Don Coryell - RB as a player
Chris Peterson - QB as a player, WRs and QBs Coach
There are many good coaches who DID play and/or coach "in the trenches".
There are many good coaches who didn't do either as listed above.
What was interesting in reading about these coaches, is how many of them were great coaches of styles/positions that didn't directly correlate to what they played or coached as assistants.
There are coaches who played/coached on the perimeter who were known for having tough teams in the trenches and coaches who played./coached in the trenches who were known for airing it out and being great on the perimeter.
It seems to be more about being a person who has a good overall knowledge of the sport, knows their own strengths and weaknesses in coaching and recruiting and builds a good staff that covers their weaknesses. If you've never played/coached in the trenches, get a position coaching job under someone who has excelled at that and learn and pick their brain. If that's still not your area of expertise when you get your first coordinator/head coaching gig, hire coaches on the offensive and defensive lines that can handle that (and you can still learn from the coaches who work under you, don't let pride get in the way *looks at Manny*). Generally, whether you're a calm Tony Dungy type with no experience in the trenches or a bat**** Woody Hayes type with lots of experience there,
know yourself and don't lie to yourself about your weaknesses, and prepare for your job accordingly and you should be fine.