As more teams move to spread formations, defenses are seeing an increase in empty backfields with five eligible receivers split outside the tackles.

Charting those formations can be difficult as many are designed to introduce minor wrinkles depending on what look the defense provides.

Alex Kirby, a former college and high school coach, offered these six questions on AFCAweekly.org as a checklist for coaches who are looking to solve the problems that empty sets present.

• Why are they in empty set? Does the offense use the formation regularly, or only on crucial third and fourth downs? Do they use it every week or just against certain defensive fronts? Figuring out what the offense is trying to accomplish can trigger a pattern that leads to stopping it.
• How much can the offense do? Does the offense show an empty set and just throw a couple of quick screens? Do they run motion to get blockers out front so a mobile QB or a player on a reverse can exploit the edge? Knowing what an offense wants to be helps adjust for wrinkles you may have seen yet.
• How often do they line up empty? If a team only goes empty once or twice each game, it’s probably not something worth taking up too much practice time to prepare for. However, if they show it five or more times each game, that’s different. Gauge whether a team will go empty at random times or only when needing a big play.
• How many empty looks do they have? Is the offense giving the same empty formation every time, or is there a variety of sets and personnel packages? Can they motion and shift into and out of empty? Do certain wide receiver splits tip off whether they will shift to empty? All these things can get a jump on what teams are trying to do.
• How do they get to empty sets? Does the offense start out empty or get there by motioning the back out of the backfield? This will determine how much time a defense has to check into an empty set look. If a team comes out with five wide, they could just be testing the defense to set something up for later.
• How are you tagging the empty sets you see? Just because there is no one in the backfield, it does not mean they all have the same purpose. A two tight-end or two wing back empty set is much different than five wide. Recognize that what a team shows one week could just be building toward what they will do against you.