19. Craig Morton
Morton was a starter for the Dallas Cowboys for many seasons. He also won a Super Bowl with the franchise. But just because a player wins one doesn’t mean they’ve played well in the playoffs. That’s true in Morton’s case because he singlehandedly cost his team another win. This time he played for Denver against his old team in Super Bowl XII.

The quarterback picked the wrong day to have one of the worst games of his career. He failed to deliver and finished with a QB rating of zero. Morton completed just four of 15 pass attempts for 39 yards and his four picks were costly (via Sporting News). If this happened during the regular season it would be bad enough, but he picked the biggest stage of all to have a meltdown.