There are 11 offensive players on the field at any given time, and nine of them are important. But the other two, the quarterback and running back, are a little more important—maybe a lot more important.
Yes, it all starts with the offensive line, and a great receiver can single-handedly reshape a defense just by where he lines up. A versatile tight end can cause matchup nightmares, and sometimes an H-back or fullback can be the X-factor that decides the game.
But the passing game runs through the quarterback, and the running game runs through the running back.