However this is only marginally better than discarding everything.
For example if the player had a suited 10 and king, with no other cards of that suit, nor a 9, jack, queen, or ace, then the player should keep the two to a royal flush. By discarding it the players odds of forming a flush are 'penalized.' Sometimes penalty cards can affect borderline plays. The discarded suited card would be called a flush penalty card because it could have been used to complete a flush. For example if the player had 3 to a royal and 4 to a flush the correct play is to keep three to the royal, discarding the fourth suited card. However for those who must play near perfectly here is my explanation, 'A penalty card is a potentially useful discarded card.
In my opinion beginning players should not use a strategy that considers penalty cards. I just rewrote my explanation of penalty cards.