Lets talk about Cover 1. The defense is also known as the man free scheme. This is the toughest coverage you you can call on defense because the defensive backs get to play tight. I call it the "You got him and I got him" defense. There will only be one deep defender who is allowed to read the QB and that is the (Free Safety).
There are some things you should remember about the coverage to be effective. The most important thing is, when you have a man, stay on that player and stay in coverage. If your receiver/tight end/ running back goes to block, that places the DB covering in the run fit. An example of this is when a receiver crack blocks on a defender, the corner back needs to replace.
Another thing to remember is the leverage you play matters. If the receiver lines up wide (outside the field numbers), the DB should start inside leverage as a press or off coverage defender. We can talk more about weakness of the cover 1 scheme shortly
4 Versions of Cover 1
Cover 1 Robber allows the defense to bracket a receiver that is dangerous. When you see coaches on offense try switching the positions of the play makers to get match ups against weaker defenders in the pass game, a defensive coordinator can make a robber or bracket call. The issue is you may lose a defender in the run fits because you have two defensive backs focused on same receiving threat.
Cover 1 Hole is still a man free concept with one safety dropping down into the middle hole. That safety is there to read the QB from 8 to 10 yards in depth. The safety is also a primary run defender to help in the box. The safety will not double or bracket any particular receiver, he will mirror the quarterbacks throwing motion and defend passes from the middle of the formation.
Cover 1 Spy/ Rat is used for teams that have quarterbacks that can make plays with their legs. Athletes like Michael Vick, Pactrick Mahomes, and Russell Wilson have beat so many teams with their legs so defensive coordinator wanted to be able to play tight man coverage and keep track of the quarterback. This particular cover 1 concept helps contain the running QB.
Cover 1 Normal/Bandit again is a form of man free coverage. The difference is that the linebackers are playing a 2 on 1 concept on the running back. The linebackers can double team the back or one linebacker can take the running back when he releases to his side and the other can free up and play the short hole