I know Denver started out 6-0, but am I the only one who thinks they might finish 10-6 or worse and not even make the postseason?

The Colts will almost surely be the #1 seed.

New England #2, either Pitt or Cincy as #3 and the other likely to get a wildcard. San Diego is right behind Denver with a game to play against the Broncos to try and catch up.  Denver still has games against the Giants, Colts and Philly, all of which they might easily lose, plus the annual road game at Kansas City (nicknamed the annual “How is it Denver is losing so badly to this terrible Chiefs team?”)  This does not include the fact that the Ravens are right behind Denver and won the head-to-head.

Denver has in no way locked up a playoff berth.