A nice Eddie Fields idea.
Have your ‘invisible deck’ resting on top of edge of the pool table – tell the spectator you have reversed a card in there as a prediction. Now take another deck and scatter the cards face down on top of the pool table. Then – have the spectator hit the cue ball off a few. The ball eventually ends up near a face down card. Show the card – this will be the spectator’s selection for the trick.
Now – take the ‘invisible deck’ and show the reversed prediction card in the deck. It will be the same as the spectator’s selection.