KC is -3.5 at Denver. Denver is undefeated at home. Insane?
It is the way this season is going. It is hard to tell the pretenders from the contenders. This game is an opportunity for one team to establish themselves as a contender. If KC loses, they may not even make the playoffs and with a win, DEN will be taken more seriously. If KC wins, everyone will assume KC is still KC and DEN isn't what their record says they are.
The betting line tells you where the money is going, or at least where the Books think the money will go. People are not believing in DEN, just like the Pats and IND and a few others. It is understandable but may or may not be reality.