The defense has done a job good enough to win just about every game. They have only allowed 20+ (21) points once this season, the best in the NFL as every other defense has allowed a higher total in at least one game.
If we had even a decent offense this team would likely have at least one or two more wins. The offense is the crux of the problem with this team and will be so for the rest of the season.
How many times this year has the offense left the defense with a short field and the defense has either held the opponent to a FG or stopped them completely.
It really doesn't matter how many yds they give up on the ground in a game or through the air. What really matters is how many times they let the other team find the endzone.