The cover 3 defense is a zone defense in which there are three deep defenders usually the safeties and a linebacker however there are numerous ways and formations the cover 3 is ran out you may see a corner back drop back as well it all depends on the team. If the linebacker you have to go back is slow you might want to use the corner but if you have Brian Urlacer or E.J. Henderson type of middle linebacker dropping the linebacker won't hurt you. Each deep defender covers a third of the field. The rest of you backers and db's will probably have the underneath assignments with the weak side and strong side linebackers covering the half of the inside the hash marks the corners would be covering the flats and attempting to force the receivers to the middle where the line backers are or completely out of bounds. This is done by jamming.
When to Use the Cover 3
When a team is passing all over you or perhaps burning you deep having three deep guys help big time. Their main job is simple don't let anybody get behind you allow everything to be played in front of you. React to the football and keep an eye on the quarterback. So if you notice the other teams offense getting a lot of big plays through the air and making quick decisions you might want to sneak in the cover 3.
Beating the Cover 3
Attacking the cover 3 is simple especially if you have a decent line to protect for your quarterback. Usually you would like about 2.5 seconds. The sweet spots on the cover 3 would be shorter routes ones good for 5+ yards or so. This means slants quick dumps to the tight end or the running back will usually get you positive yardage. If you have an aggressive mine that still wishes to go deep well you can try stacking the receivers to the outside and putting them on vertical routes. Two receivers on one deep defender is what your looking to do. This will usually give positive results as most safeties are likely to be confused. Also sense the defense is in zone and watching the quarterback so they can react. Having the quarterback pump fake or look off his hot route would give you positive results try pump faking or looking in a direction that you know won't be there. The defender seeing you looking or pump faking may react but you really want the reaction of the defender guarding the hot route in which if he is watching you may get him to sit or react towards the pump fake area.
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