Hey, something that I've found with this version of the game is that the keys on defense work pretty well. If you have an idea on what the offense is going to do or have a particular receiver that's hurting you, you can key on that and shut it down.
Not real sure to be honest. I've only ever used it on a running back that's tearing me up. It seems to work. But you can also key to different plays, like run or pass. If you get it right, you'll probably make a good stop, but it's no guarantee. On the other hand, if you're wrong, you'll get burned.