4-2-5 Defense and FS Rule in General Alright, just putting this out there since I see a couple people with this as their defensive playbook. This defense is NOT banned. It is legit. However, I ask that you guys be extremely mindful in how you use it. This defense already has 8 guys in the box and has a lot of speed on the field since it's basically a nickel package. I don't want to see anybody crashing with the FS in this defense since in this formation, he is a safety valve and truly is the last line of defense.