Sorry to snip this particular part of your post, but it cuts to the heart of all this armchair talent evaluation.
The simple and inescapable fact is that what you or I see in preseason games does not amount to much at all. The player's performance in practice is far more significant, given how many hours of it there are, in player evaluation than a few meaningless plays in an exhibition game.
Please don't talk about 'flashing' ability. This is the NFL, they all have potential, they all have their moments, but that's not what NFL careers are built on.