Sensational KC D not sustainable

Kansas City's defense is contributing more than 14 points per game to its final scoring margin. David Eulitt/Getty Images

While the offensive improvement with new coach Andy Reid and quarterback Alex Smith is getting a healthy share of the accolades for the Chiefs' surprising 2013 turnaround, the real headline lies on the other side of the ball. The 2013 Chiefs defense is off to a blistering start. So good, in fact, that warning sirens should be blaring in every corner of Arrowhead Stadium.

Defenses that have dominated in similar ways to the Chiefs have a bad history of fading late in the season and in the playoffs -- with one notable exception.