Change, as a certain newly minted president has suggested, can be a good thing. But sometimes, change is simply disruptive and damaging.
But in finding a replacement for defensive coordinator Rex Ryan, the Ravens would be best served to stay in-house.
The notion that Harbaugh needs to "hire his own guy" ignores certain facts, one being that the current Ravens defensive system was good enough to rank No. 2 in the NFL this past season and also that there are a couple of "Harbaugh guys" already on the defensive coaching staff.
Ryan, as a new head coach, could certainly take some of the current Ravens assistants with him. However, some defensive assistant coaches, such as linebackers coach Greg Mattison and secondary coach Chuck Pagano, were hired by Harbaugh. Mattison and Pagano have experience as defensive coordinators at the college level. Mattison once coached for Harbaugh's father, Jack, at Western Michigan. Pagano was Ravens safety Ed Reed's position coach at the University of Miami.
Right now, the Ravens are getting over the disappointment of their defeat in the AFC championship game, and while they know change is inevitable, both among the coaching staff and the roster, they are hoping those changes will be minimal. This is a team that needs to be tweaked, not turned inside out.
The departure of Ryan, which will certainly create some need for change assuming he takes a few Ravens assistants with him, will be traumatic enough. Elevating a coach that the players are used to - plus one who is likely to retain some of Ryan's successful defensive scheme - would create a level of comfort for the defense. And keeping that unit on track is essential to another Super Bowl run next season.