The middle group as mentioned is a mix of linebackers, tight-ends and also running backs. > That middle ground is probably not best suited for any role Modern NFL is very specialized. You have linebackers of various sizes who are used in situational conditions (passing vs running downs), and also vary in size/height based on the defensive scheme. e.g. A linebacker in a Cover-2 based defense is probably lighter/faster vs a larger linebacker used in a 3-4 defense.