I agree with TigerMonk. Keep Daniel Jackson, you should always keep a player who improves THAT dramatically in one pre-season. It shows he has drive, desire and work ethic to improve. I don't know if decision making or skill consistency can improve, but having a player go from no in the best 22, to possible B&F winner is very rare, and shows the above qualities. For a team that seems to struggle with the mental aspect of AFL football, trading someone off who seems to have a great mental ability is something rare.
Just my 2 cents.