I was tempted to include breakout star Alexander Johnson for transforming a Broncos defense that has skyrocketed from 28th to third in Football Outsiders' metrics since he entered the starting lineup in early October. But he wasted away on the bench for nearly 40 percent of Denver's games, while the other players on this list have been standouts throughout. Kuechly has been his typically brilliant self, teaming with breakout sidekick Shaq Thompson as the league's best linebacker tandem. While the Vikings' secondary has slipped, Kendricks is the beating heart of a front seven that has returned to heights of 2017. A playmaking machine, Kendricks has been a menace behind the line of scrimmage as a run-stuffer and blitzer while polishing up his pass-coverage skills. Perhaps the most versatile defensive star in football this year, Collins is the only player to earn a Pro Football Focus grade of 90-plus in four games. He has stuffed the box score to the tune of six sacks, three interceptions and two forced fumbles to go with eight QB hits and seven tackles for loss.