The main storyline here is turnarounds: Chargers righting the ship and Chiefs going off the rails.
HOWEVER if you've been watching the careers of Alex Smith and Philip Rivers, it's actually the opposite: Smith started terrible but stayed devoted to the craft and is now one of the best playmakers in the game not only with his arm but with his legs.
Rivers on the other hand was prodigious from the start of his career, but never had much in the way of arm strength, and although SD has been winning, the notion that Rivers is a deep threat is laughable. He's also a sitting duck for the blitz.
I simply do not believe the Chiefs have ever been in danger of losing the division -- they are by far the class of it. This shouldn't even be close.