Top five defensive position groups

Everyone loves player rankings. NFL Network's top 100, voted on by the players themselves, is always going to generate some gripes and disagreement -- as will ESPN's #NFLRANK, set to be release later this summer. And while both of those projects are useful at gauging individual talent, they don't delve into the broader position groups who make life nightmarish for opponents on a weekly basis. Using both past production and future performance as barometers (which incorporates new additions this offseason), below is a look at my five best defensive position groups for the upcoming season. You can find my breakdown for the best units on offense here.

Seahawks secondary

Projected starters: Safeties Earl Thomas and Kam Chancellor, cornerbacks Richard Sherman and Cary Williams

Key reserves: Will Blackmon, Jeremy Lane, Tharold Simon, Tye Smith

Quick hit: In a league that's making it harder than ever to play pass defense, the Seahawks' secondary continues to find ways to limit even the best quarterbacks on a near-weekly basis. Thomas and Sherman are the best players at their respective positions -- and part of the reason for that is the way they work in tandem, with Thomas patrolling the middle of the field while Sherman plays a heavy dose of Cover 3. Chancellor's role is to be a steady physical presence against both the run and pass, which is exactly where he excels. The starting cornerback spot created by Byron Maxwell's departure in free agency would have likely been filled by Lane, but a major arm injury and torn ACL in the Super Bowl has left his availability in 2015 up in the air. Williams -- cut by the Eagles this offseason -- could serve as a fill-in starter until Lane is ready to return.