I am not 100% sure, but as far as i know, a player is banned everytime he collect 5 yellow cards.
But the number is a bit tricky, because 2 reasons:
First of all, the card count is never reseted, so your player might have received 3 cards a season ago, and he will be banned as soon as he collect 2 new cards this season.
And secondly, the game does NOT recognize each competitiom as individuals, cup, league and WCC are put in the same bag, you can receive a card in a cup.game and you player will be banned for the next league match.
