A nickel defense is typically played when the opponent uses three receivers in the lineup. A "dime" defense (four cover corners) is typically used when the opponent lines up with four wide receivers.
With the evolution of rule changes, teams pass more often than ever. They also use three receiver sets more often than ever. But they don't always use them. For example, in the red zone, it is less likely. Conversely, on your side of mid field, with a lot of distance to go, with more room to maneuver, chances are much higher.
Given a two wide receiver set, the lineup is simple. Spoon and Woolen at boundary corner. Love (or Diggs) plays directly on the tight end (if he splits or is in motion).
Nickel is a different circumstance. As a head coach, you have to weigh the options for a three-receiver set.
1) Spoon and Woolen at boundary with Bryant at slot.
2) Spoon and Woolen at boundary with Love at slot.
3) Jackson and Woolen at boundary with Spoon at slot.
You are tempted to put your best eleven players on the field, relative to the capability of the alignment that you are facing. Personally, with respect to the capabilities of a three-receiver set, I believe option 3 puts your best eleven players on the field.
Then, as a coach, you have to ask yourself, "What do we do if a given corner is injured and has to miss a few weeks?" It is inevitably going to happen.
Taking all of the above into consideration, it is just plain STUPID to not get Spoon up to snuff at nickel. It is a force multiplier. It creates more options, more capabilities, more flexibility, more diversity. And it sort of reveals a person's relative lack of understanding, an inability to conceptually grasp this sport, to think that the team should do otherwise. Great coaches add tools to their toolbox. They don't remove them.
