When Eagles linebacker Mychal Kendricks went to the front office at the end of last season and asked to be traded, it was more than just a player disgruntled with his playing time looking for a new home. It was part of the evolution of the NFL that has seen linebackers, or at least a percentage of them, become endangered species, foraging for snaps like dinosaurs poking at the ice for sprigs of grass.
The true base defense in the NFL now includes at least five defensive backs – nickel coverage – in order to contend with the proliferation of spread offenses in which opponents employ multiple wide receivers, snaky tight ends and fleet running backs in their passing games.