5. Stone Johnson

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This Olympic sprinter was brought on the Chiefs in 1963 to return kickoffs. During a preseason game, he got absolutely leveled. He was paralyzed instantly and died eight days later.

6. Jason Sehorn

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Entering his third season, it seemed like Jason was poised to be a star for the Giants’ defense. But then in a preseason game against the Jets he went down with an ACL and MCL tear from which he never truly recovered.