On current gen, by default they have the QB automatically move and throw the ball. This is because there is an option in 'Controller Layout' called 'Auto Throw'. This is set to 'On' by default. You need to turn this 'Off' if you want the QB to just stand there for a moment or two in the pocket when you do not hold the left analog stick in any direction as you hike it. I turn this option 'Off' so I can do this. It's subtle, but important in a long game.
If you notice, when you drop back in a pass play, you will notice that the receiver icons appear. However, notice there is no receiver icon for the (X) button on ps2 ((A) button on xbox1). Hold down the (X) button (ps2) or the (A) button (Xbox1) while moving the QB in a direction to scramble on a pass play by moving the left analog stick in a particular direction.
So, if I am hiking the ball on the right hash mark on xbox1, with Auto Throw set to 'Off'. I hike the ball on a pass play don't press anything for a moment or two as the QB stands in the pocket after dropping back a few steps. Then, when I sense the pass rush coming and there are no receivers open, I hold down the (A) button on my xbox1 and hold left on the left analog stick. By holding down (A) [(X) on ps2] while the the pocket, the QB will go into a scramble run. To pass again, just let go of the (A) [(X) on ps2] button and press any receiver icon button. You have to depress (A) [(X) on ps2] before pressing the icon receiver intended. The icons will be grayed out while scrambling and holding down the (A) [(X) on ps2] button, but will re-appear when the button is depressed and the QB will go back to the drop back stance ready for the pass attempt. There usually isn't enough time to scramble, then depress the (A) [(X) on ps2] and still be able to bring up the pass icons again and pass to a receiver. You have to be quick to do this.
Hopefully this answers your question.