Like many equipment alterations, this one comes from Nike, who made the switch after the 2005 season to a better material. The old pants, which had a distinct shine to them, carried water weight and were hotter than the current pants, which are duller but breathe more and wick away sweat.
The old pants were carrying more than two pounds of sweat by the end of a game, football equipment coordinator Tino Dominguez said. Meanwhile, the new, thinner material wicks water away much better and is much more functional for the players.
Take a look at the difference between the pants in 2005 on Matt Leinart and 2009 on Matt Barkley:
 
