There’s a lot of good information in the thread already, I’ll try and summarize it and highlight the keys.
The QB usually communicates 3 pieces of information when lined up under the center.
- The snap count. This is typically established in the huddle and can vary quite a bit based on the creativity of the coach/QB and the awareness of the offensive players. It can commonly be on the first sound (quick count), on the 1st, 2nd or 3rd signal (usually “Hut”, “Hike”, “Go” etc.). When time is short the QB can yell a code which negates the previous agreement and tells them to go now. The “Omaha” example above is the most well known.
A tricky QB might further disguise the snap count by instructing a team to snap the ball on a nontraditional sound, perhaps the color “black” catching the defense on it’s heels when they think the QB is audibling. Further complicating things is the “silent count” in which a team snaps the ball on some agreed upon point, usually a head count of 3 or just allowing the center to snap whenever he’s ready and having the offense watch the ball.
- Line calls. These are essentially the QB trying to either diagnose a defense’s plan by interpreting their presnap alignment or assigning a defender to be the key for a play. This varies a lot and is specific to every offensive system. In some cases these duties are shared amongst the QB and the Center, with the QB calling out what he sees for the WRs and RBs and the Center calling out what he sees for the Lineman. Most plays have prearranged solutions to address every expected defensive strategy, and it’s critical that the team be on the same page about which solution to employ. When a defense lines up in an unconventional orientation it can be impossible to clearly distinguish what player should be treated as a priority to block or option, the offense solves this by labeling someone verbally.
Good QBs and Centers are better at guessing this than others and some offensive schemes are better prepared to react to the unexpected than others. This is perhaps one of the most important parts of the game and one least understood by the fans. Casual fans often talk about “audibles” and their coaches and QBs use or lack of use of them and there’s no end to the stress over it, however what most fans are really angry about are the line calls.
- Audibles. This is when a QB reads the defense and sees a wildly unexpected look and/or a very advantageous mistake by the defense. Teams will have a limited number of “audibles” in their gameplan. It’s essentially a mini play book that the offense must memorize, perhaps 6 plays of varying use. Perhaps 2 runs to either side and 4 passing plays which can be used in any personnel package. Some coaches use audibles and some don’t. Some veteran QBs are allowed a lot of freedom to audible, while inexperienced or less aware QB are restricted from ever using them. This drives fans nuts, even though they really don’t understand the nuances of it.
QBs traditionally indicate an audible by using the well known “Red 32!” “Red 32!” format. The color is used as the code which activates the audible and the number is the indicator of the play they are expected to use. This is dramatically oversimplified and is what teams tend to use at the high school and college levels, but it gives a idea of how it works. Suppose a defense lines up with small personnel to defend the pass, typically called the “nickel” or “dime” package with extra safeties and corner backs. They also array their lineman in a blitz look, showing that they intend to attack the passer. A QB might immediately call an audible to a running play best suited to defeat this. He’ll yell “Red 32” activating the audible and the number 32 would perhaps indicate a off-tackle run to the right. If the QB has diagnosed the defense correctly and the offense has made the proper line calls this will typically lead to a big gain. In contrast, if the QB had yelled “White 32” nothing would have changed they would have run the play called in the huddle. And there the chess match begins, because defenses will often show one look to intentionally confuse the QB or force him into an audible that they believe they are prepared for.
NFL teams audible far less often than fans tend to believe. Offenses prefer to be proactive in their play calling and not reactive, and reading a defenses intentions is rarely clear cut. An audible is most commonly used to get out of a bad play, as opposed to getting into a good play. When a QB typically audibles he’s trading a potentially disastrous play for a safe play with a modest gain. The occasions are rare when a QB is able to audible into a situation that leads to a huge gain since that would indicate a grave failure on the defenses part.
- Hot Reads. This is not typically something that’s called at the line, but it’s a feature of almost all offenses that impact or are impacted by the 3 points highlighted above. A hot read is a situation that a QB and WR can simultaneously deduce without communicating as the play is snapped. For example, if a defense chooses to blitz it’s linebacker at the snap the QB and WR should both see this happen. The WR is taught to abandon whatever his previous instruction was and run a quick slant route into the area that was just vacated by the linebacker. The QB will take 1 step and fire the ball into that spot. This happens fast and is difficult to master, but elite offenses with veteran players tend to excel at it.
This is relevant because it will usually be dictated in large part by what the QB shouts out as his line calls. When he, for example, identifies number 57 as the “Sam” he’s telling his team that if this guy does one of a few possible choices then they are to react with a hot read accordingly. It’s essentially the same strategy as the old fashioned “Option run” but with passing. This of course incorporates a lot of nuance. The QB might identify the “Sam” linebacker which tells everyone to pay attention to the “Mike” next to him. The defenses also know about this strategy and may blitz a LB in order to induce this reaction and subsequently drop a lineman into that vacated zone or have the cornerback play a hard inside technique to block the WRs path.
Hot reads are another feature that many fans misunderstand and tend to conflate with the idea of an “audible”. Some offenses use this more than others, and some defenses are more susceptible to it than others. All of these strategies discussed come with a fair amount of risk since they introduce uncertainty into an outcome. The ability to incorporate all of these strategies seamlessly is what sets great QBs, great teams and great coaches apart from one another and being effective with them tends to make your standard playbook all the more effective because it forces a defense to play more conservatively and predictably.
The NFL is interesting because in most ways every team runs the same plays, many fewer than what an outside observer would assume, but these plays can be adjusted ever so slightly in infinite and creative ways to make them unique. The difference between teams tends to lie in that 10% variance and the closer you get to the fringes the more subtle it becomes, but in that subtlety lies a lot of opportunity for those precise enough to capitalize.