The tricky part of zone coverage is the technique of field-scanning both before and after the snap. The quarterback wants to gather the most information about the defense pre-snap as possible but he must be careful not to give away his intentions. In zone coverage defenders are taught to read the quarterback and react to his movements. If Chad Henne stares down a receiver, the defense will collapse and take that option away. However, a great quarterback can use his eyes to move the defense and thus open up space for his receivers. One example is former Michigan quarterback Tom Brady, who now plays for the New England Patriots of the NFL. Brady is a master at knowing where his receivers will be, and he will use his eyes to move safeties by looking at a secondary option, directing them toward that receiver, thus opening up his primary target.
In zone coverage most of the quarterback reads will come after the snap. Although a quarterback may be able to read zone coverage and narrow down the possibilities before the snap, he will only truly know the coverage once he retreats back into the pocket and sees how the defense reacts. Zone coverage is more fluid than man coverage because there are multiple ways to disguise it and rotate into another zone coverage, such as a cover-2 rotating to a cover-3. This is done by lining up in a cover-2 look with the deep safeties, then at the snap dropping a cornerback into a deep zone and shifting the underneath coverage to compensate for the cornerback's now voided short zone. In other words, no zone coverage is definite upon a pre-snap read. These late changes are designed to throw off the reads of a quarterback, and that's why post-snap reads are so important in defeating zone coverage. Late shifts and rotations also throw off quarterback timing because he takes longer to diagnose what a defense is switching to. The longer time needed to diagnosing the defense will cause him to hold on to the ball longer, and thus give the pass rush more time to get to the quarterback. The key for Henne, which will come with time, is for him to recognize what the defense is rotating into. Once he gets more repetitions, the indicators of those rotating coverage's will become easier for him to pick up and he won't hold the ball too long, which he is prone to doing at times.
Vision and quick thinking are the main skills in reading defenders and coverage's. These skills are essential when Henne has to read a specific area, react to the defender's position and hit the most open option. It is essential he knows how each of the routes in the play book compliment each other, who is the primary target, and what is the read progression. An example of a zone read in a specific area would be a high-low flood-combo pattern with the receiver and tight end complimenting each other's routes to stretch the cornerback who is covering that short zone. The receiver runs a fade route to force the cornerback to the top of his zone and a tight end will run a quick out pattern to stretch the defender's responsibilities. When Henne is reading a short zone defender, he must first pick up that he has short zone responsibility, then quickly anticipate what his assignment will be. Since he is playing zone, the defender must cover the receiver until he has vacated his zone high, so Henne must read the clear area at the bottom of the zone and hit the option sent out to exploit it; which is the tight end.
This is an example of "keying" a defender. "Keying" basically, means to isolate a defender in his zone and defeat him with a single pass route or a combo pass pattern. The offense defeats an isolated defender by using multiple receivers to flood his zone which gets him out of position and opens up a pass route, such as the example shown above.
As I stated in the cover-2 zone article, offensive coordinators will attack a two layered (short and deep zone defense) with a multiple layered pass attack. The result is that receivers will get more spacing and can attack the area between the linebackers and safeties as well as the short zones. I suspect you will see more plays called such as this once Henne becomes seasoned and mature in his reads because it requires him to scan the entire defense instead of keying a zone to attack. This past season it was much easier for Henne to key an area and have complimentary routes run in that zone to open up an option for him to throw to. For example, Michigan ran a good amount of motion, zone floods (multiple receivers in one zone), and short zone busters with Braylon Edwards. This strategy allowed for Henne to limit errors by limiting the amount of reads he had to make.
Here's a daily schedule for the rest of the Chad Henne series:
Wednesday: reading man coverage/defeating straight man coverage
Friday: reading combo coverage/defeating cover 3 zone
Monday: defeating rolling coverages/defeating cover 1 coverage/blitz reads
Next Wednesday: Quarterback fundamentals/sight adjustment/blitz reads/Chad Henne 2004 evaluation