There have been quite a few black quarterbacks that kicked around the league without doing much. Aaron Brooks, Jeff Blake, Tony Banks, Charlie Batch, Jason Campbell, Rodney Peete, and Byron Leftwich to name a few. Some might argue Dante Culpepper would make that list if it weren't for Randy Moss. Fitting into whatever system a team has plays a big role in their value. Some players are re-signed year after year to fill a niche rather than retaining what little skill they might have. The average or below average players you are talking about are the rule not the exception. They all can't be Andrew Luck, Peyton Mannning, Tom Brady, whomever.