WRs should always know about coverages. If you are out there and you just run your routes and don’t care how many safeties there are or what the corners are doing you are not playing to your full potential. You have to be identifying the coverage and the defense just like the QBs, now what exactly should WRs be looking for before the ball is snapped?
The first place their eyes should go is the safeties much like QBs. Identify if there is 1,2 or 0 safeties. Now what that tells you is the different options a defense could be in. 1 safety could mean either Cover 1, which is man for you and the corner, or Cover 3 which is a zone concept where you want to attack the sidelines at least from a QB standpoint. 2 Safeties lets you know it is probably some kind of Zone or it could be 2 Man. In Cover 2 you want to attack the middle of the field as a QB and Cover 4 you want to attack underneath as a QB. WRs need to understand that. But how do you know which is which? That’s when you have to look at the corners. The corners are what come second. If the corner has his eyes on you, it is probably man. If he is looking at the QB or the ball it is Zone. The reason you have to understand this, is because if you can understand the holes in the defense, you will have a better idea of when you will get the ball and the openings the QB is looking for.
WRs need to know defenses, you will be second QB on the field and you will have much better chemistry with your QB if you can find holes to sit in. That is why Edelman has such good chemistry with Brady, he was a former college QB so he gets it. He is not a very big guy, but he is able to sit in holes and find openings in defenses due to understanding coverages.