For years, Mike Zimmer was quietly able to design a defense that befuddled offensive coordinators, hidden from the spotlight as a play-caller in Cincinnati. But after he finally landed a head-coaching job in Minnesota at 58 years old, his colleagues took notice of the traits that helped turn the Vikings from a five-win outfit in 2013 to an 11-win team two years later.



First, they took his double-A gap blitzes, implementing the scheme Zimmer became most known for. Then, after Zimmer’s beloved defense ranked No. 1 in both points and yards allowed last season, the fellow coaches spent an offseason studying why it worked. Coaches around the league began taking cues. Some took bits and pieces of Zimmer’s scheme. Others — as many as 10 or 12, Zimmer estimated — employed plans that looked almost identical to the Vikings’ base defense. The more teams used it, the more offenses learned to beat it. Coaches studied it more because they played against it...