Although it may not seem like it after their Week 1 performances careened in opposite directions, the San Francisco 49ers and New Orleans Saints had something in common heading into the season. After years spent at the bottom of the NFL's defensive rankings, both teams took a dramatic leap forward in 2009. The Saints went from 26th in Football Outsiders' 2008 DVOA Rankings to 14th a year ago, while the 49ers went from 18th to third.
And yet, fans of each team should not expect their respective defenses to play at such a high level this year. There's a fatal flaw in the way those teams rose up from the defensive underground that will be close to impossible for them to reproduce in 2010. It's not just a teamwide thing, either; we can go ahead and pinpoint the exact players whose contributions are unlikely to be repeated in these upcoming 15 games.