They are the farthest players away from each other on the football field.  A team's two cornerbacks don't interact on the field much during a game, but each has an enormous effect on the other.

A shutdown corner on one side and a liability on the other does absolutely nothing for a defense.  

Darrelle Revis with Lito Sheppard was nothing special.

Cortland Finnegan combined with Nick Harper was a disaster.

To truly have a dominant secondary, two talented cornerbacks must combine.

It's when you get the Charles Woodson-Al Harris combination a defense really gets scary.

Here are the rankings of the cornerback duos worst to best in the NFL this season:

http://bleacherreport.com/articles/519147-nfl-power-rankings-week-11-rankings-all-32-cornerback-tandems

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