One of the hardest sets in football to defend is the cluster or stack set. Spread offenses utilize this set to get the defense’s outside linebackers in run/pass conflicts. Unlike a traditional 2×2 set, the defense has to adjust to the width of the receivers. Stacking them creates width, and width creates the conflict.
Spread teams rely on the open “B” gap to build their RPO’s into their offensive gameplan. By stacking the receivers out wide, the defense is forced to adjust. In a two-high system, the player in conflict (usually the Will LB) has to choose, cover down to his receiver or hold tight to the box. If he stays close to the box, the offense is going to throw the quick screen and create a 1-on-1 open field tackling matchup with the safety or corner. In most cases, the defense wants to avoid this as much as possible.
On the other end of the spectrum, if the defender widens to the cluster set, the offense has a 4-1 box and a clear running opportunity. Versus a two-high system, there is a great chance for the offense to part the field like the Red Sea for a big gain. Ask any offensive coach, a 4-1 box is a magical thing.
In the image below, Penn St. is running an Under Front and “hips” it’s Sam LB to the strength (“hip” refers to the OLB aligned on the outside hip of the DE). In most RPO style offenses, this is a clear pass read. The Sam has to honor the run read and step to his gap. Even with zone away and a gap exchange with a “heavy” DE (in this set the DE has dive), the Sam has to take a step towards the box. The QB is taught to read the Sam’s path and throw the screen.
Penn. St. is most likely in a “Cloud” coverage (Two Read) and the safety is bailing on the snap. Easy pickings for any decent offensive coordinator. It’s a conflict of philosophy; the offense wants 1-on-1 matchups and the defense wants a plus-one. In order to create a six-man box and protect against the run, the defense has to spin to single-high, but to keep a plus-one in pass distribution it has to stay in two-high, something has to give. MatchQuarters explores the options.