Famed Michigan State University Defensive Coordinator Pat Narduzzi calls the Cover 4 Defense the “Mother of all coverages.” Often mistaken for the prevent defense, the Cover 4 is actually a match-up zone concept that divides the defensive secondary into four zones, split equally between two cornerbacks and two safeties. It can be adapted to fit nearly any defensive alignment or scheme.
The Defensive Front
Teams can run Cover 4 out of the 3-4 (three down lineman and four linebackers), 4-3 (four down lineman and three linebackers), nickel (five defensive backs), dime (six defensive backs), or quarter (seven defensive backs) defensive sets. Teams can rush as few as two men in prevent situations. New England Patriots coach Bill Belichick has even used speedy linebackers as pass rushers in his Cover 4. In any case, the scheme calls for the linemen to stop the run first and rush the passer second. It's not uncommon to see a defensive lineman dropping off into coverage in Cover 4 blitz packages.
Linebackers and Extra Defensive Backs
Because they're protected by the coverage umbrella behind them, Cover 4 linebackers and extra defensive backs can afford to play the run first. They line up 5 yards from the line of scrimmage and play downhill, meaning they read the offensive line’s blocking scheme and attack the line first. They cover the shallow zones in passing situations, looking to cut down slants and shallow crosses over the middle and screen passes. Numerous blitz schemes are designed with the Cover 4 over the top, which gives linebackers plenty of opportunities to make big plays in the backfield.
The responsibility of the corners is simple in the Cover 4. They typically lock up in man coverage with the wide receiver in front of them. The defensive scheme determines what coverage the corners play. Some Cover 4 corners play press coverage, where they can dictate the wide receivers release from the line of scrimmage. Others play softer, giving the receiver a cushion to prevent against big plays. When a receiver runs a quick slant or shallow crossing route, the corner passes him along to a linebacker or nickleback to the inside and plays zone coverage near the sideline.
The safeties have to diagnose plays quickly and make big plays when opportunities present themselves. The safeties read the second receiver on their side of the field. If that receiver run-blocks, the safety becomes an additional man in the box to help against the run. If that player runs a short route, the safeties provide help over the top for the cornerbacks. Finally, if the second receiver runs downfield, over 10 to 12 yards, the safety will lock that man up in man coverage. The safeties also have to watch for deep posts and crossing routes coming from the opposite side of the field.