The 3-4 defense and the 4-3 defense are the two most common defenses used today. The 4-3 defensive scheme Four defensive linemen and three linebackers make up the 4-3 defense. The D-line positions are as follows: There are two defensive tackles on the team. The DTs guard the inside of the line. They can also stand up and rush the passer from here. Next is the DE or strong side defensive end. He is responsible for rushing the quarterback off the edge. Then there is the PI or pinch runner who comes in when there is a need for extra depth on the field. Finally, there is the OLB or outside linebacker. He is usually the biggest player on the defense at 250 pounds or more and he makes up the other side of the pass rush. He will often drop into coverage to follow receivers downfield. The 3-4 defense Three defensive linemen and four linebackers make up the 3-4 defense. The D-line positions are again as follows: There are two defensive ends on the team. One is called the LE or left end and the other is the RE or right end. They work exactly like their counterparts in the 4-3 defense with one exception: They do not get any help from either of the tight ends attached to their sides. Then there are the two linebackers. One plays close to the D-end on which he is attached while the other covers the middle of the field.