Coaches in most sports are vastly overrated. Except for Bill Belichick. And in general, football coaches are the most important, because football is the most complicated of the American major sports. The only hard part about managing a team like the Yankees is dealing with the media, personality clashes, and George Steinbrenner. Tactically, a solid knowledge of baseball is all you need, nothing extraordinary. That is not to say that coaches don't make any difference. They definitely set the tone for their teams, but players always make the most impact.