If you have researched the success of every past Super Bowl winner, a solid backup QB is one thing you would see more than expected.
Joe Montana had Steve Young, then when Steve Young took over, his backup was Steve Bono (a solid backup).
When the Miami Dolphins went undefeated in 1972, starting QB Bob Griese got injured early in the year. Backup QB Earl Morrall took over and led Miami all the way to the Super Bowl until Griese finally healed up.
And in the 1997 and 1998 NFL seasons, when the Denver Broncos went back-to-back, John Elway got hurt a couple times during the regular season.
His backup was Bubby Brister of all people, and he went undefeated went under center in The Mile High City.
So as you can see, backup QBs are very, very important.
That being said, who's better; Trent Edwards or Josh McCown?