I also have seen this bug in some of my games.. A player that is not in the game appears in one of the plays. For me only happened in plays in which he was defending some adversary attacker. This bug might be meaningless, but might also be very important, since the player executing the defense can determine the result of the play.. The whole defense system might be afffected, if it's considering a bad reserve player instead of the good starter that is really in the game...