Competition is a great way to increase the energy of a practice. It is a great tool to inject some passion and get players to increase their effort level, but it must be used wisely.
Football practice is tough. The focus on necessary skills and the endless repetitions of these drills can cause players to lose enthusiasm and get sick of practice. When this happens players' effort falls, and their attention to detail drops. The best way to combat this is by creating competition within the practice plan.
There are a variety of places where competition can be incredibly effective, but it does not fit every setting. It’s important to make sure that the players have a firm grasp on the skills you are asking them to use when they go into competition. Competitive drills are not the place to learn a skill, they are the place to apply the skill.