The turnover among NFL head coaches each offseason is well documented. Raiders head coach Dennis Allen was the first coach fired this season, and there were seven head-coaching changes this past offseason, with just seven of the 32 current coaches hired prior to 2010.
With head-coaching changes often come coordinator changes, as a total of 22 new coordinators were hired this past offseason. The impact of coordinators can be driven by new personnel, a new scheme or -- in some cases -- simply a new personality overseeing similar personnel and running familiar concepts. On occasion, a change in voice is precisely what a team needs, much more so than an overhaul of players or a new X's-and-O's approach.
With most teams at the quarter mark of the NFL's regular season, here's a look at a handful of coordinator changes that have made a substantial impact early on.
Vikings offensive coordinator Norv Turner