In football, because of the different sides of the ball, coaches often specialize in one thing, e.g., linebackers, quarterbacks, special teams, etc. The idea is that these positions require specialized knowledge acquired over years of work.
Could a linebackers coach take over a team's passing game? It's possible, just as it's possible that an accountant or IT person could take over a company's marketing department. But I'd prefer that someone who specializes in the passing game, and who has a deep understanding of it, handle that.
Similarly, I'm certain the CEO of Pepsi or Coke prefers to have an experienced marketing professional handling the brand's marketing efforts. Let the experts in accounting or IT focus on those areas.
Consider USC's football staff. In addition to the head coach, director of operations, and strength and conditioning coach, there are coaches for:
- Tight ends
- Defensive Coordinator/Defensive Line
- Running Backs/Special Teams Coordinator
- Passing Game Coordinator/Wide Receivers
- Offensive Line
- Offensive Coordinator/Quarterbacks
- Defensive Line
And this list doesn't include the team's graduate assistants. This is at the college level, of course, but the NFL coaching rosters are almost identical. [Here's the Chargers' coaching roster, for example.]
But with this level of specialization comes a great deal of accountability, which is why so many assistant coaches/coordinators are fired even as the head coach survives.
It's the opposite in basketball, where if the head coach is fired, his assistants sometime stay. During his head coaching career, my Dad had a rule that he made sure his assistants understood from the start: "When I go, we all go."
For him, as for most coaches, loyalty was critical for his staff. There's nothing worse than an assistant coach waiting in the wings for the head coach to get fired.
Over the last several years, basketball staffs have begun to resemble those in football, with assistants focusing on (and responsible for) a particular area of the game. In Golden State, we took this approach, with Tom Sterner essentially serving as the team's defensive coordinator, Jim Boylen as the offensive coordinator, Keith Smart as a sort of "quality control" coach, and David Fizdale managing player development
Coaching staffs in basketball have grown, of course. I remember a few years ago, the Mavericks had a dozen or so coaches, including head coach Don Nelson, assistants Donnie Nelson, Del Harris, Charlie Parker, Larry Riley, and Sidney Moncrief; player development coaches Morlon Wiley, Paul Mokeski, Ro Blackman, Brad Davis, and Greg Dreiling; and a coach for free throw shooting, Gary Boren.
But it's not only a staff's size that's changing. More and more head coaches are assigning specific responsibilities to their assistants. Last August, for example, Tom Thibodeau was hired in Boston to help with the team's defense. No where in the team's official announcement of his hiring did it mention what exactly he'd be responsible for. However, it was clear based on its tone and content what Tom would be doing. ["Thibodeau has helped his team finish in the NBA's top 10 in team defense 14 times."]
But unlike football, where it's clear to everyone what a coach is responsible for (and posted front-and-center on the team's website and in its media guide), basketball teams prefer to keep it more general, though that's changing.