Not doing anything as an assumed leader can be seen as bad leadership. The quarterback is the assumed leader.
He's got control of the ball. On defense, you might have a secondary assumed leader. He get guys motivated while the offense are on the field. There's something called team psychology, and a good leader can help a team. And sometimes, it's people with your mentality who become the leader. You walk around on the sidelines, tell everyone they are grown adults with families and bills and they need to run their routes because their jobs depend on it.