Make no mistake, audibles are a necessary function of every offense. They get the team out of plays that have little potential and into plays that are low risk and perhaps can result in a big play. However, no matter how good the audible packages are, they are only as good as the general under center who can use them. Some schools such as Michigan State have changes called down from the coaches box to the sideline and into the quarterback. However, at Michigan Chad Henne is the man on the spot to read the defense and make the call. Not only does he have to read the coverage types but he must also be aware of potential blitzes, the defensive front, the balance of the defense and the tendencies of the defense. Like I've said before, Henne must contrast the out lay of the play called in the huddle to what the defensive alignment shows. If the offensive blocking scheme cannot compensate for the amount of defenders to the play side, a running audible must be called. A good example is for any one who's played the popular Madden Football 2005 video game, you can alter the direction of the running play before the snap and it's basically the same theory on the real gridiron.
Now how does a quarterback go about doing this? Of course I don't know how Michigan works their audibles but one of the most popular forms is in the cadence. Since quarterbacks are suppose to only get their reads under center, it makes sense they make their checks while they are there as well. Most teams will have what are called "live" and "dead" colors in their cadence meaning live is a check, and dead is a mere part of the cadence and changes nothing. We will use maize as the live color and blue as the dead color. If Chad see's a potentially bad situation, he can change the play by using the color "maize" in the cadence, he will look to both directions like always and yell the color in the cadence so everyone on offense can hear the call. Once the offense hears the maize call, they will then listen to the rest of the cadence to key in on the new play. Most systems use numbers in the run game to designate the back running the ball and through which hole, also they number the routes in the passing game so the numeric call after the live color will signal which routes to run. Of course if the call is blue, the offense will execute the play called in the huddle and numbers mean nothing.
One very important key for the quarterback is to always switch a called run play to another run play and a called pass play to another pass play. Not only is it potentially confusing but the receiver splits may be different in a run play and thus it would throw the timing off if it were checked to a pass and vice versa. Also consider that the blocking schemes are universally different in a run call and a pass call. Henne must also consider the formation, personnel grouping and game situation (down, yards to go and score) to select the best play to check into. Another point coaches will stress with quarterbacks is to check down to a simpler play, however this doesn't necessarily mean a more conservative play. Audibles puts enough pressure on the offense to adjust as it is and adding a more complex play will only increase the pressure which can lead to breakdowns. Another point would be that if a play is changed, the cadence called in the huddle doesn't change; for example if they play was called to go on "two", the new play will go on "two" as well. The last key for a quarterback is to be aware of the play clock, taking too much time attempting to check off a play can result in a delay of game penalty or having to burn a timeout.
This process like any other improves with time. As you see in the NFL, former Wolverine Tom Brady (Patriots) is constantly changing the play at the line of scrimmage because he has experience and a great knowledge of defensive looks. Experienced field generals like Brady know what to look for and see more than younger quarterbacks and thus have more trust in changing into better plays and out of bad ones. Quarterbacks must also use the time used in film study to expand on the characteristics of what they look for in a defense. Through time in the film room, Henne can better see potential mis matches with opposing defenders, defensive tendencies and how defenses react to different offensive looks. Knowledge in this area will better help him select the best play and opportunity to use an audible.
A very effective tool that doesn't necessarily change the play but changes receiver routes is sight adjustment. Sight adjustments are designed to defeat any type of coverage by checking to a route based upon a defenders alignment. The quarterback and receiver use a type of communication prior to the snap to change a route. The most common form of communication is using hand signals, and each team will usually have up to four different routes to defeat each type of alignment a defender will show in coverage: outside shade (figure one), soft shade (figure two), press shade (figure three), and inside shade (figure four).
Generally the receiver will make the initial signal to the quarterback based on his read of the alignment of the defender, the quarterback then makes the final decision on if the receiver will run the sight adjusted route by sending back a yes or no hand signal. Usually a quarterback will accept a receivers signal if he reads a one on one matchup. Teams that feature deep routes in their sight adjustment package will also read the safeties to take advantage of deep positioning of the secondary. Again you video gamers know this type of audible in Madden and NCAA Football 2005 where you can "hot route" before the snap into a different route. Overall sight adjustment is a low risk, high percentage audible that doesn't always necessarily gain big yardage, however it allows the offense to take what the defense gives it, take advantage of mismatches and establish a rhythm offensively.
Overall, any form of an audible whether it be in a complete play change or a sight adjustment is geared toward giving the offense a upper hand against the defense. Through proper coaching and execution by the quarterback, the skill of changing a play will dramatically improve the efficiency and consistency of an offense while avoiding broken plays. Though this skill is developed and polished over time, through proper film study, knowledge and increased confidence, a young quarterback such as Chad Henne can develop the skills to master this process that is very vital to an offense.