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The best free safeties cover the field like no other player can.

They often start from the back of the defensive formation as the last line of hope on a deep pass. If that free safety has the requisite skills, he'll move quickly from "center field" to either sideline. He'll have to take up massive parts of the field, especially in Cover 1 and Cover 3 concepts. He'll also need the field intelligence to quickly read run plays and react just as fast to assist as a force defender.

He'll be asked to help his cornerbacks with bracket coverage on top receivers and tight ends, and disguise that help so the opponent doesn't have time to adapt. He'll also be asked to work as a slot defender at times, based on the scheme. There's a tremendous list of things to do for the best free safeties, but if you think it's tough for them, imagine how things don't work when a player who finds the speed and coverage requirements overwhelming gets put in that spot.

All of a sudden, there are second- and third-level blown coverages. Offensive game-planners know they have a sucker play with deep vertical routes and seam routes and deep posts. The burden on the other members of the secondary can be too much.

It's a rare player with all the requirements for the position, and in today's NFL, where passing is paramount, it could be argued the free safety spot has never been more important.

NFL1000 scout Kyle Posey has been watching the NFL's safeties all season, and he has his player rankings and scouting reports based on the following criteria:

Coverage: 30 points. How well does this player cover from the defense's third level? Can he take receivers to either side, and does he read routes well enough to know where to go in time to get there? How well does he work with his cornerbacks in zone coverage? Does he have the physical ability to create contested catches, deflections and interceptions?

Recovery: 30 points. With that much ground to cover, it's inevitable that every free safety will be out of position once in a while. How well does he recover from a false step? When receivers come into his area from blown coverages elsewhere, how well does he pick up the mess?

Slot Performance: 10 points. When he's asked to play in the slot, how well does this player adjust his coverage requirements to the option routes and close coverage at this alternate position?

Tackling: 20 points. This covers everything from tackling in deep space to run stopping to the ability to blitz. How well does this player wrap up and stop the play once the ball-carrier is in his area?

Position Value: 8 points. This considers positional importance when comparing grades across other spots on the defense. Free safeties are given 8/10 points, making their top possible grade 98.

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