private List <GameObject> _cards; // If I were you I'd have a Monobehaviour class "Card" or so, which each card has, then you can replace BoxCollider2D with that and access functionality for cards in the deck from here
public void OnPointerClick(PointerClickEventData data)
{
var topmostCard = _cards[0];
_cards.RemoveAt(0); // remove the topmost card from the deck
DoSomethingWith(topmostCard); // and have it played
// For example move it to the center of the table... and have it affect the game logic
}
public void OnPointerClick(PointerClickEventData data)
{
Destroy(this.gameObject);
}