Unlike in years past, there's no obvious successor for the defensive coordinator position - which has always been among the most important jobs in the Ravens' organization.
There was a time when Brian Billick had the luxury of passing over Rex Ryan to hire Mike Nolan as coordinator. Such a plethora of options isn't a luxury the Ravens will enjoy this offseason.
This isn't an indictment of the current staff, but the Ravens don't have an obvious successor in place. For the most part, this is a matter of experience. Some coaches have been in the organization for only a limited period; others have a focused and limited expertise that might preclude them from a coordinator position.
The defense was Ryan's baby. He found a way to take what Marvin Lewis and Nolan scribbled in pencil and trace over it in ink, perfecting it, putting a stamp on it that would be recognized across the league.
To continue the tradition of excellence, coach John Harbaugh needs a devoted disciple of Ryan's system - someone who can garner the respect of a veteran-laden defense - or failing that, it's time for Harbaugh to put his fingerprints on the team's last untouched surface.
Harbaugh retained only six coaches when he took over one year ago, signaling a desire to put his own people and his own philosophy in place. It only makes sense that he would continue in that fashion, hiring someone from outside who fits Harbaugh's vision, not merely someone who aspires to replicate past Ravens defenses. With turnover inevitable, it would be a mistake to find a coach to match personnel.
Rather, it's wiser to find a coach from outside who can then adapt and shift the pieces as needed.