If I blow a pitch (strike called a ball) I will generally say something just loud enough for the batter and catcher to hear. One of my buddies uses the line: Happy Birthday, batter!
To the catcher I am saying: I blew it, that was a strike.
To the batter I am saying: If the ball is at that same spot again, it's a strike.
Naturally, this is not something that you want to be doing several times a game.