He missed so far this year:
(for the games where he missed part of the game, I am just going to calculate the total game yards, which would actually help out the argument that they aren't as low as 27th)
2nd half vs. Giants = 435 total yards
Cowboys = 417 total yards
Bengals = 325 total yards
3 Q's vs. Pats = 496 total yards
Eagles = 330 total yards
So adding up these numbers and taking the average to figure where the D would rank without Jimmy, the average for all these games is 400.6 total yards per game.
Now to see where that falls in terms of total team defense. Looking at the chart and the average yards team defenses are allowing a game, The Mom Gene is actually correct, we wouldn't be ranked 27th.
We'd actually be ranked 30th. .2 yards ahead of the Browns D. And like I said above, the numbers are worse if you would look at it per quarter since the Giants and Pats went off without him in the lineup and I can't find a per quarter yardage output to make the analysis more accurate.