Newcomer/player returning from injury to watch: Tyrann Mathieu, safety.
By signing Mathieu, the Chiefs got themselves a stud at safety who can really play just about anywhere in the defensive backfield and hugely improve the defensive unit against the pass and rush. More than all that, though, Mathieu brings a swagger to the Chiefs that was absent. They had plenty of star power in their defensive ranks, but perhaps there was more pomp than pop, as a unit that featured the since-departed Justin Houston and Dee Ford (Eric Berry played sparingly) allowed 421 points, ninth-most in the NFL and the highest total among playoff-bound teams.