For every busted knee, every time a guy gets his head knocked off, every time an ankle is twisted or a wrist sprained there is a guy on the bench eager to seize the opportunity to play.
More often than not, that opportunity is short-lived.
But sometimes tragedy leads to the discovery of a guy like Brett Favre, who replaced Green Bay's Don Majkowski when he tore his ankle up in September 1992 and started every game for 15 years after that.
So, is there a "Magic Man" in the making this season, who, when given an opportunity, will be so good the team never looks back?
But, there certainly is no shortage of season-ending or long-term injuries to go around this year, and one man's bum knee spells opportunity for another. Let's take a look at some who face huge opportunities on the heels of an injury to a starter.