Pro Football Focus has more than its share of both supporters and detractors of how it goes about grading NFL players. They break down every snap for every player, and while there are general agreements on what's seen by naked, untrained eyes who don't put the time and investment into its system that PFF does, there are other evaluations that seem to come out of the blue. While there's occasional guesswork on a player's particular assignment on a given play within its scheme, those of us who've watched and studied nuances of the game, or those who've played it, can usually identify how many jobs were done correctly.