The Vikings are having all kinds of issues with their passing game, preventing them from keeping defenses honest.
The NFL is a copycat league; observers talk about it every year. If a team is having success and another team finds a way to stop them, the other teams are going to look to see what happened in that game and use some of the same strategies in their game plans.
That is currently what appears to be happening to the Minnesota Vikings. They started out 7-2, but things seemed to get derailed a bit when they took on the Green Bay Packers in Week 11.