Without commenting on the rest of your post, I disagree with this 100%. There absolutely is such thing as injury prone players. They are "kitty's" and there is always something ailing them almost on a weekly basis.
And yes, injuries do happen. And so do players like Freddy thy used to play through broken feet, ribs, legs, etc. there's also people like Terrell Davis who couldn't see at all in the Super Bowl but during a few plays but still went out there because the team needed him. Then there's players like Jack Youngblood and Ronnie Lott that have done much more on serious injuries than players could imagine.