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Cornerbacks have been challenged to lock up the sport's best receivers since the invention of the forward pass. Through the eras, physical dominance defined the best pass defenders, from Dick "Night Train" Lane to Willie Brown to Lester Hayes to Deion Sanders.

But if you want to be one of the game's greatest cornerbacks in the modern era, you have to meet unique challenges. No longer can you simply bump against your receiver and wrestle him to the ground. Ever-favorable offensive rules have hamstrung cornerbacks, forcing them to play deep balls with perfect technique or risk a game-changing pass-interference call.

Moreover, the route concepts modern corners must cover are more advanced than ever. Floods, switch releases, double slot combos…the list goes on. In an era when most cornerbacks must be able to switch between man and zone coverage—at times on the same drive—coordination with teammates is at an all-time premium.

So, the modern cornerback must bring a unique skill set to the table. He must be lightning-quick to deal with vertical routes to the boundary. He must have instant recovery speed to handle all kinds of angular routes. And he must be stout in the run game. The days of cornerbacks making plays in the defensive backfield and "business decisions" as force defenders are over.

The best corners of this era are among the greatest we've ever seen, precisely because they are so challenged on every play. NFL1000 defensive backs scout Ian Wharton has been watching every team, and he's ranked all the game's outside cornerbacks (we'll have a separate article ranking primary slot defenders) with the following criteria:

Coverage: 25 points. This is based primarily on outside coverage but also measures slot coverage. How well does this player take his receiver through the route? Is he equally adept at man, zone and pattern-reading coverage? How well does he backpedal and turn? Can he keep pace in bail coverage?

Reaction: 25 points. Does this player have the reactive intelligence to run a receiver's route with him, or does he waste steps? How well does he time his jumps, deflections and interceptions? How many opportunities does he miss or make by being in the right place or one step out of line?

Recovery: 25 points. If a receiver uses a step to get away from this defender, how well and how quickly does the corner recover? Does he lose his receivers on comebacks and cuts? Is he too aggressive to match a more elusive wideout step for step, and how many steps does it take him to get back on track if he does make a mistake?

Tackling: 15 points. After a catch is made, how often does this player allow yards afterward because he can't close and wrap up? Is he a useful force defender against the run, and if so, how quickly does he adapt from coverage to run defense?

Position Value: 10 points. A score that takes positional importance into account when comparing grades across other spots on the defense. Cornerbacks are given 10/10 points, making their top possible grade 100.

Make sure to check out all of the NFL1000 rankings from the 2017 season.