Where are some good references for learning the strengths and weaknesses of different defensive formations and alignments, and learning terminology? I'm a casual fan, been watching football for 40 years but I've never dove deep into recognizing coverages or knowing which ones work best in which situations.
I know basic terminology, but some of it I don't. For example 4-3 Under Trail Mix. I know that's 4 lineman and 3 LB's and I'm pretty sure the Under refers to how the lineman line up, but I don't know what Trail Mix is. More importantly, I don't know really what the strengths and weaknesses are.
Also, how are blitzes handled in the game? Is it just different terminology within the play calls, or is it something that's handled in gameplanning or coach style?
I guess what I'm looking for is to spark a discussion on defensive strategy, both in-game and game-planning. Or maybe find a real good primer on the subject.