1. A team is a complex system.
2. As Neil Johnson puts it in his 2007 book Two’s Company, Three Is Complexity, complex systems share a number of common features: The system has many interacting agents, their behavior is influenced by feedback and they can adapt, the system is open to environmental influence, the system evolves in a way that gives it a sense of being alive, it exhibits emergent phenomena that often are surprising and extreme, it has no controller, and "the system shows a complicated mix of ordered and disordered behavior."
3. You can analyze long term trends of a football team, just like you can analyze long term trends of weather. But you can no more isolate or accurately predict any one part of a team than you can any individual rainstorm.
4. Not all trends matter at all times. When you are analyzing how a hydrogen molecule will behave in a cup of water, you don't need to worry about Heisenberg's uncertainty theory or that an atom is not indivisible. We can use Rutherford's model of an atom. But just because Rutherford's model works in one situation, does not mean it is true, or that it will work in all situations. The same is true for a football team...just because team z is built this way, or that team y responds like this in b situation, does not mean the same holds true for team a.
5. As stated in point 2, a complex system has no controller. A coach can provide direction, and may be responsible for certain individual decisions, but ultimately any team is outside the control of any coach or GM.
6. When two complex systems interact, (like in a football game), the interaction changes the system. As stated in point 2 complex systems are influenced by feedback, and environment, and will adapt. A football team will change both game to game, but also "in game", and those changes are based not just on the team itself, but the team being played and other outside factors, (weather, score, field conditions, etc). Hence, any team can beat any team on any given Sunday.
In other words...no one knows anything.