which is funny because belichick is a defensive minded coach
looking at the remaining teams in the playoffs you have the patriots (belichick), broncos (fox), falcons (smith), seattle (carroll) with head coaches with a defensive background - you have SF (harbaugh), GB (mccarthy), houston (kubiak) with offensive backgrounds and then baltimore (harbaugh) with a ST background that has coached both sides in his career, but has put in more work with the defense
i think there is a good mix of defensive & offensive backgrounds in the HC position .... i think you are seeing more teams try to find lighting in the bottle by hiring the "offensive genius" or stake to someone with a pedigree for working with a QB ..... doesn't guarantee success though