you make some decent points but,
first of all, nfl players make wayyy too much money, they play a game. why should they make more than say doctors? or politicians?
life ending injury? thats highly unlikely, being a cab driver is more risky than being a football player.
and who says you cant get fired from a job for no reason? you can fired from any job for pretty much any reason. it may not be fair, but thats how jobs work.