I've said it before, I'll say it again. Let the rushers get their yards. As long as the quarterback is ineffective and opposing defenses stay out of the end zone, the Packers will win.
That #2 ranking was severely skewed by the fact that the Packers' special teams were so atrocious last year, opposing offenses were working with short fields several times a game. The defense gave up fewer yards than average because other teams had so few yards to cover.