The slot blitz is a great way to stress an offense. You’re bringing pressure with a faster defender, and that leaves the protection and the quarterback with less time to respond.
Not to mention, because of the speed of the blitzer, he can come from a greater distance and still get home. That allows for more effective disguise.
Generally, an offense’s worst blocker (a running back) has to account for the slot blitzer, often after checking for another defender elsewhere. Or, the quarterback has to see him and be ready to throw hot. And sometimes, if there aren’t any built-in hots, the success of the play is dependent on a sight adjust and a receiver breaking off his route.
A lot can go wrong from the offense’s perspective against a well-executed slot blitz. And that can lead to big plays for the defense.
One of the keys to this type of pressure, particularly against a 6-man protection, is to make sure the running back is occupied. He’s the blocker most likely to be accountable for the slot blitz, generally on a dual read where he has to look elsewhere first.
This play from Chris Shula’s Rams Defense in their Week 7 win against the Raiders was a great example of this. First, notice that the Rams were in dime personnel (6 DBs) to get more speed on the field:
Now look at the pressure front. The Rams were showing blitz with 6 defenders on the line of scrimmage, and the Raiders had 6 in to protect: