All season long it's been the Broncos and Bengals who've battled New England for AFC supremacy.
Recently the hot topic of conversation is that the Steelers might be the team the Patriots are most afraid of, to the point that the Pats may have even lost to the Jets on purpose in order to keep Pittsburgh out of the postseason (I think that's crazy--there's no way Bill Belichick decided to give up clinching the No. 1 seed with a week to go because he's afraid of a potential second-round playoff opponent who may or may not even get there).
As it sits now, the Steelers could well be out. Denver and and Cincinnati are both using backup quarterbacks. Who's the top threat to New England returning to the Super Bowl?
The Chiefs were once 1-5. Now they are 10-5. Nine straight wins is a pretty big deal in the NFL (sidebar--Arizona has also won nine in a row, and I'm expecting them to take the NFL title). Kansas City has allowed just 12.3 points per game during their winning streak. Do I think they'll win the AFC? No, but they have as good a shot as anybody else does.