For the last decade if you wanted to try out complicated defensive setups in Madden’s practice mode, you would have to do so using 2 controllers: 1 on offense and 1 on defense. If you didn’t use 2 controllers the CPU would control the offense in practice mode causing the ball to be snapped right away before you would have time to set up your defense.
EA Sports addressed this issue in Madden 18 and made the CPU offense smart enough to know not to snap the ball until you are done setting up your defense.
Here is the exact wording EA Sports used to describe this fix:
When a user is on defense, in Practice, the AI will not snap the ball if it senses the user making defensive adjustments. This gives plenty of time to practice exotic defensive setups without having to be worried about the AI quick-hiking them.
This should allow for more unique blitz concepts since now everyone can try out complicated defenses. It also allows our Madden School Unlimited members to practice our Madden 18 defensive ebooks without having to worry about using a second controller.
This was a fix implemented for the more serious Madden gamer who makes multiple pre-snap adjustments to the defense before the ball is snapped. If you are a more casual gamer who just picks a play and makes no adjustments, you will not notice any difference.