Chiefs and Texans rank among most improved offenses and defenses

Chiefs QB Alex Smith and Texans DE J.J. Watt have powered their respective units down the stretch. Getty Images

Consistently strong play on both sides of the ball has helped the Cincinnati Bengals, Arizona Cardinals and Carolina Panthers combine for a 32-4 record through Week 13. The Seattle Seahawks and Kansas City Chiefs are taking a different path to late-season relevance, overcoming sluggish starts to climb sharply in their conference standings.

December's race to the 2015 NFL regular-season finish line will showcase teams in varying stages of performance. Some teams will sprint, gaining speed all the way. Others will limp. With that in mind, I've compiled the five offenses and five defenses that have shown the greatest statistical improvement so far this season. Some of these units belong to true contenders, such as Denver and Seattle. Others belong to teams fighting their way toward respectability.

To analyze offenses and defenses, I divided every unit's performance into two six-game blocks and then ranked each unit within each block. Expected points added (EPA) per game was my metric of choice, for reasons explained here. Once the rankings were set, I calculated how many spots each unit moved up or down from its first six games to its subsequent six games. For example, the Chiefs' offense ranked only 27th through six games, but it has ranked fifth for games seven through 12. The plus-22 change in offensive ranking represented the largest gain for any offense in the league.

The Chiefs also ranked among the top five on defense. (No wonder they've won six straight.) Which other teams have made the most significant jumps? Let's dive into the lists.

Most improved offenses

1. Kansas City Chiefs (+22)
Games 1-6 rank:
Games 7-12 rank: 5th

The Chiefs were supposed to be finished once they lost running back Jamaal Charles to a season-ending knee injury in their fifth game. Instead, they have transitioned into one of the NFL's best teams. Alex Smith ranked 32nd out of 33 qualifying quarterbacks in Total QBR through six games. He trails only Carson Palmer over the past six games, tossing eight touchdown passes without an interception. Receiver Jeremy Maclin has seen his production spike of late, but the Chiefs are 2-2 when he reaches 100 yards receiving. Kansas City has the look of a team that started slowly, stayed the course under a strong head coach and improved as the season progressed.