The value of a college football player can fluctuate like a 1990s tech stock.
Rivals.com listed Arizona State's Sam Keller as the No. 8 quarterback in the nation earlier this month during our rating of the top 25 players at each position.
Keller now is enrolled at Nebraska and will be a spectator for the 2006 season. He is out of a job and off the chart in our first College Football Stock Exchange of the season.
We'll run the stock exchange every week to update our rankings of the top players at each position based on how they perform each weekend.
Only in this case, the rises and falls started before the season began.
Back when we rated Keller as the No. 8 quarterback in the nation, we also listed his likely backup – Rudy Carpenter – in the No. 16 spot. Now that Carpenter has beaten Keller out for the starting job at Arizona State, he fills Keller's spot at No. 8 on our list.
Since Keller fell off the chart, Southern California quarterback John David Booty replaces him in the Top 25.
The rankings will measure a player's overall skill level and game-day performance.
One awful game won't necessarily cause a player to free-fall down the list. For example, Troy Smith is certainly one of the best quarterbacks in the country. If Smith struggles against Texas, he is still a great player. He may drop a few spots, but Smith is a blue-chipper whose stock should remain near the top of the charts.
Conversely, one outstanding game won't automatically put a player on the list if he hasn't performed well all season.