If Sports Teaches Character Then Why Do 78% NFL Players Go Bankrupt?

Sports Illistrated Magazine reports that things don't go well financially with retired NFL Players.  Chris Chase, sums it up on Yahoo Sports:

"Within two years of retirement, 78 percent of NFL players are bankrupt or in severe financial distress. Unlike Rocket Ismail, most of those players can't blame it on the negative karma associated with getting a bear hug from Michael Irvin.

How is this possible? The minimum salary for rookies in 2009 is $310,000. That jumps to $460,000 for two year veterans. How can men who earn so much have so little after retirement?"