from what I have read, players with the special abiliti play like a player one star higher than their current star in specific situations. so you have a 4* corner specialist that will play like a 5* when taking a corner. Nothing too special it seems as it is most likely a way to get you to waste tokens thinking they are much better at something when 1 star rarely makes a difference. Look at some defenses that have 1 or 2* players and they keep clean sheets, so does anything matter in this game?