If there is one continuing theme around the National Football League, it is that change occurs on a yearly basis. Veterans who haven't performed up to par are replaced with cheaper, younger alternatives.
It even happens to some of the best players who have ever stepped onto the field.
For example, the Chicago Bears made the decision to go with rookie Jon Bostic over future Hall of Famer Brian Urlacher. The end result was the conclusion of one of the greatest careers in modern league history.
San Francisco traded in the consistent play of one Alex Smith for a high-octane and high-upside youngster in the form of Colin Kaepernick.
Meanwhile, St. Louis bid adieu to long-time running back Steven Jackson in order to go with a myriad of youngsters at the position.
These stories could make up a novel that makes Atlas Shrugged look like a Where's Waldo? book.
This slideshow will focus on nine veterans who simply must step up in 2013 in order to keep their jobs throughout the duration of the season and into the following year.
All contract information provided by Spotrac.