What is the role of the NFL head coach? First, let's be clear on why I limit this to the NFL: head coaches have important recruiting roles in college sports. This is not the case in the NFL. The major areas of responsibility are as follows:
- offensive play-calling
- defensive play-calling
- special teams play-calling
- instant replay requests
- practice planning
- game planning
As best I can tell, 1 and 2 are run by the offensive and defensive coordinators; the head coach can overrule a coordinator, but if the head coach is a better play-caller then he should call all of the plays. 3 is basically a subset of either offense or defense. 4 is almost a science based on clock, score, and field position. 5 is best requested from the booth, where the assistants have their own televisions. 6 is typically run by position specialists. 7 is basically a grouping of offensive plays and defensive plays (e.g., let's run the ball early, then throw an occasional deep ball; let's sit back most of the time, then blitz when #80 comes in).
This leaves #8. You would have to analyze why each play succeeded or failed and see where the breakdown occurred. Comparing these breakdown stats to a benchmark would help show who who is over-performing. A report could say that a certain play is expected to gain 4.5 yards, with a 1 yard standard deviation, while the actual average was 5.7 yards. The next step would be to attribute the improvement or decline to certain factors.
But wait. Isn't the role of the GM (general manager), often a successful ex-coach to handle hiring/firing? If the GM is excellent at this, then maybe he could handle hiring and firing assistant coaches as well.
As usual, maybe there is another factor at work. Maybe the coach serves the role as speculator, taking on the reputation risk for the team owners and executives who are interested in having long-term careers. The big shots sell their short-term accountability to the coach, who is richly rewarded when things go well and quickly shown the door when they don't. A coach with a good track record may actually just be good at one thing: identifying which teams are set up for success already.