I say this because he's had one full year to take the duties of Quarterback for the bengals, and has become a better more aware Quarterback. Near the end of last season he was putting up pretty good numbers because he took his game to the next level. With recievers like Chad Johnson, TJ, and Peter Warrick he won't have a problem finding someone to throw the ball to. Also, with the running being quite a success, defenses will have to keep an eye on Rudi Johnson and Chris Perry which will lead to some holes in the field.
I think the best fit for Carson would be Top 20, but if he plays his game right and cuts down on the interceptions..I think this kid could be quite the Quarterback. Definately very valuable in keeper leagues.