All sports share major, common elements. Both physical and mental skills must be taught. Drills must be practiced until they become automatic response mechanisms. The mental qualities of perseverance, determination and motivation must be instilled.
Football is different. There are eleven players involved in every play, unlike baseball where two, or maybe three players are involved. Hockey requires teamwork with players moving at high speed but there are five players on a hockey team compared to football's eleven. Volleyball may involve as many as three players in a given play. The sheer multiplicity of players on a football team where every player is involved in every play makes it different from other sports.

Since every player is involved in every play, any one player can miss an assignment and the whole team fails in making a successful play. There are eleven chances to fail on every play whether it's on offense or defense. On the other hand, a perfectly executed play requires eleven players doing their job as trained with no one player missing his assignment. This makes football is a very difficult and unpredictable game.

Football arguably requires more intricate teamwork than any other sport if one bases the argument just on numbers of players on the field at any given time. Because of this, balance becomes essential because of the different assignments of different positions and different physical skills required for each of those eleven positions.

The coaching challenge is how to take a given football team with all it's complexities of human personalities and physical skills and meld them into a balanced force that successfully executes, both on offense or defense.

There are no hard, fast rules for the football coach to fall back on. He will have to develop his own formula for success given the roster he has to work and the balance he needs to achieve. Does the coach favor a running game or a passing game? What proportion of the plays will be passing and running? How will the game plan and plays be scripted for a particular opponent? Does the coach emphasize a ball control game or a short yardage game? Is the backbone of the team based on offense or defense?

All these factors make football a crazy, unique game, in which anything can happen at any time and often does. Surprises and upsets are common. One player missing one assignment can blow a whole game.

Football coaches are, above all, jugglers. They must juggle twenty two players plus second team players so as to achieve a balanced, cohesive, force that successfully executes the philosophy of the coach. This philosophy will be unique to every coach and therein lie's an enormous challenge.

The ever changing complexities of this challenge from game to game and season to season makes football a unique sport. The sheer number of players, differing skills and assignments raises the number of possible outcomes to an exponential level.