In pure zone coverage techniques that involve reading the QB, there are benefits and drawbacks. to it. The benefit is the ability to see the ball and ultimately take advantage of poor throws. The drawbacks are the precense of windows the QB can hit, given the lack of sight on the WR's. I have gone into detail on this on a previous post. However, even the biggest proponents of pattern reading have certain coverages that involve players that read the QB. First, any coverage that involves corners that bail at the snap, do best to involve some type of QB read to gauge the type of pass (3 vs 5 step). Any Middle Field Coverage, involves a FS that stays in his zone in the middle of the field while he reads the QB for an indication to break.
Another drawback to reading the QB in pure zone techniques is the QB's ability to look off a defender and then throw the ball the other way. For example, in cover 3 the FS drops down the middle of the field reading the QB. The most difficult play for this player to cover is the 4 verticals (double seam). QB's are taught to look one way and give a pump fake to get the FS to break before throwing the ball to the other WR, that the FS can't recover on. This creates a problem. On one hand, you cannot tell the FS to break when he sees the ball leaves the QB's hand, this will be too slow more often than not. On the other hand, you can't give advice like "don't fall for the first fake" or the like. The worst thing you can do to a FS in MOF coverage is slow down his breaks. The effectiveness of the coverage relys upon the FS's ability to break on the ball well.
Is there another solution? Yes! The key is in finding a reliable key to read on the QB that indicates a throw is about to occur. This key needs to be present only when the QB is going to throw and not part of the pump fake. Reading the QB's eyes is not reliable in cover 3 for the FS, because he can be looked-off. Reading the ball is no good, because A, the pump fake can get you and B, waiting until the ball leaves his hand will be too slow.
The solution is to read the QB's non-throwing arm. Teaching the FS (or any other pure zone dropper) to read the long-arm is an effective technique. The FS should break when he sees the QB's arm go long (or lengthen). The typical QB does not pump-fake with his off arm extended. The only active arm in a pump fake is the throwing arm (unless the QB pump-fakes with both hands on the ball, still there is no long arm in this type of fake). The long-arm is the motion a QB makes when his off hand creates separation from his body. This separation happens in the beginning stages of a QB's throwing motion. Have you ever tried throwing the ball with your off hand stuck on your body? Try it sometime, it is pretty difficult. Have you ever tried pump-faking with your off arm extended, its possible but it will throw off your throwing rhythm. Most QB's do not have the adequate time nor patience to develop this type of pump fake.
Another benefit of reading the long-arm is the indication of where the ball is going. The further the off-arm is from pointing at you, the further you have to break, this lets the player somewhat know what angle he needs to break on the ball at. He does not have to wait to see the ball in the air to know what angle the ball will be going.
Some QB's show a clear extension of the arm. Look at Carson Palmer below:
Try this out and practice this with your players. I have integrated this into our cover three technique and seen tremendous results. QB's can no longer look us off and we have a breaking key that allows us to get in motion before the ball leaves the QB's hand. This read can be equally effective with underneath droppers and corners.