All players have listed one or more positions in which they can be used, but what happens if you play them outside these? Is it just a matter of looking at the stats and deciding for yourself if a player can be used in another position, or does the player get penalized further?
In other words; are the positions of the player suggestions by the game, or is there more to it? It would make sense if they were just suggestions, IMO. You could then use Firmino as a goalie if you wanted, but from his stats you would gather that he probably wouldn't do a very good job.