I looked at CBs using @PFF's data because I have some problems with their coverage grading system. They usually grade plays where the Cornerback isn't targeted with a +/-0, which results in rarely targeted players like Ramsey or Alexander receiving lower grades than someone 1/x

like Xavien Howard, who gets targeted more often and therefore has more opportunities to make good plays on the ball. That's why I added Snaps per Target as some kind of context, to show which players are so good in coverage, they don't even get targeted. 2/x

Top right are those Cornerbacks that are rarely getting targeted and are great at the catch point, top left are those that are getting targeted more often, but are good at defending those targets, bottom left are CBs that get targeted less but when they are, they 3/x

aren't good at defending and bottom left are the worst Cornerbacks. 4/4

Same thing for Safeties

Accidentally added a 250 coverage snaps threshold on the pictures above. Lowered it to 100 here.