I once asked a member of the Ravens organization if the team gives any credence to the player grades published by Pro Football Focus, aka PFF. I was told that they do read them but the system, through no fault of PFF’s, is flawed because they don’t have any way to understand the assignments of the players on any particular play.
A player could be dinged for a missed block for example, when in fact the perceived whiff was really a player’s attempt to cover a teammate’s blown assignment.