Types of Football Defenses
From a base 3-4 alignment, the defense overloads one side of the offense by placing as many as three of the four linebackers to that side. They might stick a cornerback there, too, or put a safety there in place of a linebacker. The object is to confuse the quarterback and the offensive linemen, forcing them to wonder: How many people (four, five, or six) are really coming at the quarterback?
The down linemen in this scheme usually engage the center and guards. Their intent is to occupy these players and give them the impression that they may be rushing the quarterback. Often, the defensive linemen merely hold their ground while waiting for the run, or they stop, peel back off the line of scrimmage (by 5 yards or so), and then attempt to cover that area (this move is referred to as short zone coverage) against a possible pass play. The object of a zone blitz is to create one or two free lanes to the quarterback for the linebackers or defensive backs who do the blitzing.