"You never really know about a quarterback until he plays in a real game"

This quote by Mike Singletary is describing the trouble of assessing a quarterback's capacity before they have had the chance to play in a genuine video game. It suggests that a quarterback's performance in method or in a scrimmage is not a trusted indicator of how they will certainly do in a real game. Singletary is emphasizing the relevance of seeing a quarterback in a real game situation prior to making any kind of judgments about their ability. He is suggesting that a quarterback's true capacity can only be seen when they are playing in a game that counts. This quote is a pointer that a quarterback's performance in practice or in a skirmish is not a reputable sign of how they will execute in a real video game.