DB: Field drills
There are varying styles of corners and safeties, so like wide receivers, it is important to know which drills may be relevant to one player and not the other. Big physical corners may not need to run sub 4.4 in the 40-yard dash or be incredible in the change of direction drills, but those could be crucial for an undersized corner.
The same could go for safety, a single high player needs to have the speed, burst, and change of direction to cover a massive amount of space. Box safety is dying out a bit, but if you want a safety who can come down and be physical at the line of scrimmage at times, you might want a player who either has the great size or has excellent short-area quickness and burst.
However, I highlight the field drills for defensive backs because it reveals so much. They show how fluid a player is in terms of being able to backpedal, turn and run, open their hips, and change direction. All of which directly translate to the field regardless if there is a receiver in front of them or not.
There is a baseline of athleticism that is necessary to play the position at a high level, and that is hard to get past. But being fast and explosive yet stiff can also cause difficulties for a player at the next level. Perhaps if you play more of a zone scheme, you can get away with that, but if your team plays more man coverage, you’ve got to be able to turn and run then flip your hips on breaks. And you’d like to see that at least somewhat on display during the field drills