One of the most difficult things to do in sports as a manager is to decide which players should play when. This is compounded in sports where there is no re-entry rule, like baseball and soccer - one you take someone out, they are done.
BUT in football, there is no such rule. Here, I think we should be rethinking substitutions, and maybe we can follow through on what Rex Ryan was thinking a couple years ago.
For Football, here is my logic. Disclaimer - I'm a fan, not a coach; just trying to think of this as a manager of people in the business world:
1. Mastery comes from talent plus practice.
2. The fewer things you practice, the more time you have to put against each one.
3. NFL coaches, through third down backs, nickel cornerbacks, and goalline linemen already practice specialization - putting in a particular player for a particular package.
4. Certain skills are more valuable at different parts of the field. For instance, having the ability to throw the ball a long distance is irrelevant when your team is at the five yard line. Being tall and able to throw over the line is less relevant when the defense puts fewer linemen on the field.
5. Making good decisions is easier when the solution space is narrowed. Entire college offenses have been designed around 'one-read' QBs to reduce the complexity. Going through progressions is a great skill of the Rodgers, Mannings, and Bradys of the world, but not a strength of say an RGIII. Rather than minimize the entire team's playbook based on the limitations of the QB, why not keep the defense guessing and having to prepare for anything by using different QBs in different packages?
6. Fresher players are better players. The proliferation of the no-huddle or lightning fast hurry-up offenses has directly correlated to higher scoring.
So, WHY NOT (for instance) put in a goal-line or a third-down QB? I'm interested to hear your thoughts, as a certain team in Philadelphia has the perfect opportunity to do this with Mr. Tebow this year - they can hide all his flaws and maximize his strengths by just making him the goal-line QB.
Baseball: Baseball has led the charge on specialization - the other day, the White Sox strategically used four pitchers in an inning. Not because of a lack of success, but because of matchups. But let's think of the next step for baseball, or a step back to simpler times? How about keeping a pitcher in the game by having him play outfield for a batter then coming back into pitch, rather than just removing him from the game? I can go into the nuance of this, but as long as a pitcher can play the field (and a lot of them can at an adequate level), I think a team can gain a big advantage here.