A good play is easy to spot on game day. It’s the decision to go for it on fourth-and-one that yields a fresh set of downs, a blitz-beating touchdown toss, or even a basic trap play, executed perfectly a handful of times, that marches your offense down the field. But while these plays unfold in the moment, it’s the weeks and even months of preparation that ultimately make them work. Good play calling is the result of repetition and trial and error without the glare of the lights or the eyes of the crowd. It’s the tweaking and the teaching and the implementation of concepts that were rolled out in spring practices or honed on hot summer days.

For some, it’s a near exact science. For others, it’s an innate feel when they are in the flow of the game. And for others still, it’s a bit of both. Play calling can be as unique as the person calling the game.”

                                   -American Football Monthly.

This quote perfectly explains the thought process behind play calling. Some call it an art, some a science. The truth is really a combination of the two. There is a definite science portion to calling plays. Coaches (good ones) will not just go out there and wing it. They study opponents tape, tendency charts, and personnel. Every team has a procedure they follow when determining what to call.  Most NFL/College teams will have multiple people in a booth charting what they see out of a defense. One person may be assigned to write down every coverage they see on a corresponding down and distance. Another may be keeping track of every blitz an opponent uses. All of that information is factored into a play caller’s decision making.

The "art" portion of play calling comes from a playcaller "feeling out the game." This statement is probably greatly overused, but every playcaller has a comfort zone. When they get a feel for the flow of the game, they generally settle into some sort of rhythm.

Now that the basics are out of the way let’s take a deeper look into play calling. There are two different types of play calling; series based and concept based.

Series Based:

A series based offensive philosophy  begins with one play,  the defining play for the offense, and a play which they run to perfection against a "base" defense. It’s the one play that will ALWAYS work against, for example, a 4-3 alignment.  They run this play until the defense changes their alignment to stop it. Then they run the corresponding play to take advantage of the change. After the defense adjusts again, they run another play designed to hurt the new alignment.

A typical sequence would take place like this:

Offense runs ISO 32 for a moderate gain. 

Defense responds by moving their Strong Safety into the box.

Offense calls ISO PA Fake. Receivers either have one on one with no safety over top against man, or the ability to settle into zones without the fear of being popped by a safety. This play is run to look exactly like the ISO run.

After being hurt by a long pass, the defense draws their safety back again , but they have their WIL (Weakside) and Mike (Middle) linebackers blitz. The idea is to shut down an ISO run or hit the QB before he can complete the PA fake.

Knowing the likelihood of a blitz, the play caller runs an isolation draw. In this diagram, the call looks like ISO Draw 34. The linemen set pass protection and then fire out. If executed correctly, the RB will slip behind the fullback taking out the blitzing linebacker and run until the SS tackles him.

I could go on with this as the series can continue with a power play, a counter, and numerous others. I hope this demonstrated  the idea behind series play calling, albeit in a simplistic manner.

Credit for the pictures goes to ESPN although I did edit them to show what I wanted.

Concept Based:

Differs from series based play calling as the offense can move from many different formations/personnel groupings in order to give defenses many different "looks." This style is not predicated on forcing a defense to over adjust or change their alignment. It quite simply attacks defenses conceptually where a series based offense would stick with similar formations/personnel and run corresponding plays.

A typical concept based drive could look like this:

Offense runs the Double Slant concept in order to attack from the short passing game. QB has a three step drop and hits the correct man based on coverage.

The offense then runs a zone stretch play from an Ace set.

An offense may then run an entire different concept, Sprint Draw Pass from I-Formation. The quarterback  fakes the draw and then hits the skinny post, deep in, or tight end shallow cross underneath.

An offense can continue with many different concepts based on what they run well, what the defense is doing, or even a playcaller's pure whim.

In the NFL,  offenses are concept based, but almost all of these offenses have series based "packages" in their playbook.

Series based playcalling works best at the youth and high school levels as there is limited time to practice, and it is prudent to run an offense that can be run with varying talent levels.

The NFL's talent level makes running series based playcalling hard to do as defense's don't always need to adjust to stop a play. The ISO series posted above can be stopped without drawing a safety into a box, linemen don't adjust their techniques, coaches play similar coverage, etc. However, there is still value to having it as part of your playbook. For instance, the Browns "Flash" package is probably series based.