Everyone talks about Carr but Gus Bradley is the most importance piece. If he vastly improves a defense that gave up the 3rd most points, had the 3rd fewest sacks and turnovers, and ranked 30th in third down defense, this team might go somewhere.
It should help the offense too if the defense gets them some turnovers and gives them better field position.
How many teams have won a championship with defensive numbers like that? Those are numbers one would expect to see from a team at the bottom of the standings.