22. Steve Young
Young replaced Joe Montana in San Francisco but defied expectations to become a legend in his own right. The three-time Super Bowl winner was one of the most effective quarterbacks that the league has ever seen. In the end, his decline was rapid but not of his own making and mercifully didn’t last for long.
He only started three games in 1999, his final season as a professional. However, in those three games, he suffered two concussions. The 49ers didn’t feel comfortable playing him and said they’d release him if he didn’t hang up his cleats. Even though the Broncos wanted to sign him, he did the right thing and quit.