See if you dont set captain, pen taker, free kick taker does it not just set the player best to do the job as it? Ive never set a player as captain n very seldom free kick. Pen taker.
Think captaincy is just a visual thing (like nationality, squad number)
I would say that contract has an effect though, players that i have on one year contract seem to lose morale all the time and play alot worse