QB stats from the past are questionable due to changes in the game. That being said--all the guys you mentioned (as well as two guys named Elway and Peyton freakin' Manning) spent their early years on terrible teams who were in such horrid shape that they had very high draft picks to use on a QB. Trevor Siemian took over for the defending champions with the league's best defense, and led them to the 7th seed in a 6 seed playoff field.