Went back through Nick Saban's 2005 book "How Good Do You Want to Be" last night and came across this passage:
Let me let you in on a little secret about football coaches: Very few of us have the skill, experience, and education necessary to motivate a group of eighty men merely with a pregame speech. Contrary to what you have seen on television or in the movies or read in books, Knute Rockne was doing something out of the ordinary in rallying the troops with a few words before kickoff.
The truth is, if you have been sending the message all week, then two minutes before kickoff doesn't matter much.
At our level, if your players are not ready to play on their own, then there's something wrong. Of course, all coaches and leaders like to give a few reminders and will occasionally play to the emotion of the game, but sometimes saying little or nothing can be as powerful as saying a lot. It's the repetitive motivating message given daily over the course of the week that has a real effect -- not a few words before kickoff.
Parents will get their message about the dangers of underaged drinking through to their children better with constant reminders than with a speech the night before prom.
Your message should be constant. A well-developed message is more effective than one motivational talk.