Unless you're the 1991 Buffalo Bills or the 2008 Arizona Cardinals, there's almost no way you'll be seen very far in the postseason with a bottom-five defense.
Both of those aforementioned teams went on to lose their respective Super Bowl match-ups, in case that was an unknown fact.
After finishing their regular season 15-1 after a 13-0 start, the 2011 Green Bay Packers seemed like heavy favorites to be representing the NFC in Super Bowl XLVI. As we've seen, they were derailed along the way by the eventual-champion New York Giants. They finished with one of the worst defensive units seen in recent memory, finishing dead-last in average passing yards given up per game, as well as leading the category for most yards given up in total.