Last year, Northwestern's defense shut down Stanford and put an early hurt on the Cardinal's playoff hopes. So many factors impact the College Football Playoff throughout the season, including defenses that can shape -- or shake up -- the final selections.
Insider has identified the defenses that, based on talent and upcoming opposition, are likely to impact the playoff chase. And just because certain defenses appear here doesn't mean these teams aren't playoff contenders. Most aren't playoff favorites, but the strength of their individual units makes them worth watching as the big games loom.