PFF grading system appears unclear

Rouxble said
They use the data that drives the grades. For example, they can watch every snap that was a loss for Trevor Penning to see how best to attack him, which would require teams to have some faith that PFF's staff is able to identify a win or loss.

To me, it's funny that one of the biggest complaints of PFF is that they don't know a player's exact assignment on a play. News flash, neither do NFL coaches watching opponents' game film. Both groups are making educated guesses, but they can still see when a DL gets driven back, or when an OT gets completely beat on a passing down, even without knowing for sure precisely what a player was expected to do.

I wish I could find it, but there was a video where multiple coaches were asked to identify the pass coverage from the same game film, and they were all coming up with different answers. Even if they differ on what they think the coverage is, they can still figure out whether a CB has the speed to recover on a crossing route, or the physical skills to jam a receiver at the line.

And some of this isn't a huge mystery. You can see from the play what the intention is. From that intention, individual players roles become clarified. And then you can see those individual players attempting to do based on the plays intention and what you would expect each individual player to do. Sometimes they do it, sometimes they fail, and usually it's somewhere in between. But football isn't 22 people randomly running around each play with secret and unconnected assignments known only to coaches. It's all generally pretty obvious.

I would say I speak largely about OL play, other stuff I know less about but I would assume for someone who understands the position or scheme, it would be fairly straightforward.

There will always be edge cases and what is more difficult to know with a great deal of certainty are the finer details of what a coach expects in terms of technique. While I understand, for example, where there should be a combo block on a zone run between two players, I wouldn't know how long the coach expects that combo block to last - is it quick or should it be maintained until a certain point, etc. And it is on this last point, to at least some extent in my experience, coaches will base a grade and that would create a divergence between any outsider grading purely on perceived outcomes.