6. Tyrann Mathieu
The Chiefs signing Mathieu to a three-year, $42 million deal last offseason was perhaps the most impactful move any team made in free agency all year. Along with new defensive coordinator Steve Spagnuolo, Mathieu helped transform a bad secondary and a mediocre-at-best defense into one of the league’s best in 2019. Mathieu continued to make clutch plays throughout the season, including in KC’s first Super Bowl win in 50 years.