Too many people are throwing around PFF grades without really understanding that they're subjective grades given out by some dude.
Historically, its been pretty hard to rate individual defensive players. But I think I have a way:
Here's how I'm looking at the data, and I think its a superior way to look at individual defensive players. I'm taking +EPA, which is an excellent objective statistic -- not like PFF grades -- and adjusting it for playing time (+EPA goes up with playing time, naturally),
Here is +EPA per snap:
|Player||EPAplus per snap|
Positive Expected Points Added (+EPA) -- The Expected Points Added attributed to a defensive player, limited to only the plays that are net positives for his team. It is a measure of a defender’s impact on the game score in terms of play-making ability. Like for +WPA, only positive plays are considered for individual defenders because very good individual defensive plays can still result in net losses in EPA. However, overall individual EPA likely correlates well with +EPA.
Here's what it look like if I look at 'big plays' - +WPA (win probability added) per snap.
|Player||WPAplus per snap|
Positive Win Probability Added (+WPA) – The Win Probability Added attributed to a defensive player, limited to only the plays that are net positives for his team. It is a measure of a defender’s impact on the outcome of games in terms of play-making ability. Only positive plays are considered for individual defenders because very good individual plays can still result in net losses in WPA. For example, a safety who makes a shoe-string tackle to stop a TD would be a great individual play, but the play as a whole would still be a net negative outcome for his team. However, overall individual WPA likely correlates well with +WPA.
Here they are multiplied together: