The Safety Blitz play is a fun play for your Safeties because it is an assignment for something that they do not get to do very often. This type of blitz can often times go undetected because the offense does not regularly see a Safety blitzing up the middle of the play.
There will be some weaknesses in the defensive secondary due to the fact that you are removing your Safety and sending him towards the line of scrimmage. Therefore, your players must keep their eyes open and look for vulnerabilities as the play develops. In other words, even if a player is in man-to-man defense, they should keep their eyes out for other receivers that have released into the field unguarded.
Teach your other defenders to be ready to rally to the ball if the Quarterback is able to get a throw off. Even though they have a man-to-man assignment, they will need to be ready to peel off of their man and find where the play is headed if the Safety is unsuccessful in his blitz attempt. Even if the Quarterback gets the ball off in time, it is still a useful play to keep the offense from relaxing and letting them know that you will occasionally bring the attack right back to them at any moment.
Pull this one out when you want to disrupt the normal flow of the offense. It can be a risky play because it may need to result in leaving an offensive player uncovered, but it is a calculated risk meant as an opportunity to get one of your most athletic players into the offensive backfield and sacking the Quarterback for a big unexpected loss on the play.