Let's start with what impact the units have on a game
45% defense (they have to stop the opposing QB and their run game, right!)
45% offense
10% special teams, including FG kicker
That's gotta be very close to correct, right?
Now we slice up the offense, which is already just a slice.
Players impact on the offense:
QB, 30%
Running backs, 15%
3 WRs, 20%
TEs, 5%
5 O-Linemen, 30% (they impact run and pass game)
This works out with math to 13-14% of impact/control a quarterback has over the game. It's gotta be something close to that.