IIRC he was trying to rush back from some type of nerve injury, it was clearly affecting him, you could see it because it was like every other throw, some would be lasers like you're used to with Dan, and some would be lame ducks and there was no telling what you would get. Its sad because I think there was still potential to squeeze some good years out of him but him and Jimmy could never get on the same page, Jimmy wanted to force his running game but we had no good backs to carry (KAJ was meh), so we'd end up relying on Dan to bail us out.
The defense was good enough that if we actually had the running game, those teams could have made noise. One more good receiver (preferably a deep threat with OJ as the possession guy and Gadsden as more of a tight end), and an actually competent running back, and who knows. Instead Dan ends his career with two of the most embarrassing playoff losses ever, the Denver one was bad, the Jacksonville one was disgraceful.