It's just something I picked up by watching who covered whom under different match-ups of offensive set vs defensive set. It took quite a while to develop the info.
Also, I think if the zones were designed on a one-size-fits-all-defensive-sets basis, you could flood a zone against at least some (if not all) defensive sets and with a smart enough QB always pass to an open receiver..
1/13/2018 10:21 PM (edited)