I posted the exact stats somewhere else, but there are at least 15 drives where either the SD D should have been on the field, or had a longer field to defend, that were lost to turnovers, fumbles, blocks, and returns.
If those drives occur normally (ie SDs kick/punt team doesn't give up a return or a blocked kick, the offense punts instead of turning the ball over), the opposing O would pickup some yards.
If they only picked up 10 yards, the SD D rank falls to 4th (just worse than Balt)
If they only picked up 20 yards, the SD D rank falls to 9th (just batter then Miami)
If they only picked up 30 yards, the SD D rank falls (this only I don't remember) somewhere around 17th.
Those missing drives are huge in the grand scheme of ranking by yardage.
SSDD