At this point, I think we're all assuming that the Falcons will eventually move to a 3-4. It's the preferred defense of new coordinator Mike Nolan, after all.
Whether that transition happens in a year or if it takes two is up for debate, but I'm going to proceed as though the Falcons will at least gesture in that direction in 2012. That could mean a hybrid defense where players do occasionally line up in a 3-4 formation or one that incorporates elements of that scheme into the Falcons' D, so it would be instructive to know who will end up where.
Before we get into the breakdown, note that the Falcons don't have every single piece they need to make the transition work. A change would also mean that certain free agents—I'm thinking John Abraham—would . The secondary could be effective in either a 4-3 or 3-4, as long as it's more aggressive, so we won't spend much time on them today. It's also possible that the Falcons will simply roll out a 4-3 again.
Now, keep in mind that the team could run a 3-4 similar to the Cowboys', which does not require a hulking nose tackle and relies more on speed and shooting the gaps. That would require less of a personnel bloodbath to get done and wouldn't require a sacrifice in the kind of versatility that's so helpful for nickel packages. Your typical enormous blubbery NT isn't awesome in passing situations.
This is my look at how the Falcons' current personnel might fit into a 3-4. Please note that it's likely to be wrong, wrong, wrong and that the team hasn't committed to the switch yet before you read this. Take the jump with me.
The Mighty 3-4
Why: Peters is almost the ideal 3-4 defensive end, in my mind. He's big, has pretty good explosiveness and has proven himself capable of going after the passer and getting after the runner. Ditto Babs, who is aging but still should fit in nicely. The two of them together could really cause problems up front.
Jerry's a big question mark. Like Peters and Babs, he's got size but isn't big enough to be a nose tackle, so he'd be better off as an end. If the Falcons can actually get him going, he could be an effective reserve at minimum.
The Falcons may have to try to trade Edwards, who would seem to be a little big to come off the edge in a 3-4 and would need to bulk up a bit to play end in the scheme. On paper, though, his run-stopping would make him a stellar fit.
There's enough depth here that the Falcons could probably get by with this, assuming they don't jettison Edwards or try him at OLB. Peters and Babs should be able to make the transition with relative ease.
Defensive Tackles: ????
This is the big question. If the Falcons run a traditional 3-4, they don't have anybody on the roster who is big enough and nasty enough to fill the 3-4. Maybe Corey Peters could if they bulked him up, but I think he'd be a better fit as an end.
There are a couple of free agents nose tackles the Falcons could try out, and they could ask Vance Walker to be the backup when they want to run smaller and nimbler. If they choose to run a less traditional 3-4 with a smaller NT, Walker could probably fill that role as well. We're not 100% certain he's coming back, though.
To me, Sidbury is the clear winner in a shift to the 3-4. He's got the combination of size, lateral agility and pass-rushing acumen necessary to play linebacker in the scheme, and he could blossom into an excellent starter if given the chance. I'd pencil him in as a starter right now if I didn't know I'd somehow wind up wrong.
Opposite him there's some interesting possibilities. If the team brings back Kroy Biermann, he could have some success. He did play linebacker in college at Montana, after all. Cliff Matthews has an enormous amount of talent and could also fit in the system, though he'll need some time to learn it.
I wonder what happens to Sean Weatherspoon. He's such a talented player in so many ways, but he's not a traditional thumper against the run game like Curtis Lofton and Akeem Dent. It won't matter if he's routinely getting into the backfield, something he's certainly capable of doing, and he could be a truly elite OLB if Nolan determines he's a fit. That's a bit of a question at this point, especially if he can't put on a little extra weight without losing speed.
Spencer Adkins is also a dark-horse candidate, though I think there's enough talent outside that they'd probably slot him inside.
Inside Linebackers: Curtis Lofton, Akeem Dent, possibly 'Spoon and Adkins
Lofton wouldn't struggle to play ILB in a 3-4, but the Falcons have to re-sign him first. He's gotten better in coverage and we already know he's capable of handling runs up the middle, should they get by our mysterious hulking nose tackle. The important thing for ILBs is to be strong and athletic, because you'll be asked to do a little bit of everything.
Dent is far less proven, but he did play ILB in a 3-4 in college and knows his way around the system. As a traditional run-stopping linebacker with fundamentally sound tackling, he'll probably start gunning for a starting job in a 3-4, assuming the Falcons don't see fit to put 'Spoon inside. My only concern with Dent would be coverage, which he isn't ideally suited for.
Adkins probably makes the most sense inside. He's fairly well-rounded and has quality athleticism. 'Spoon could also make it happen inside, but it would be a waste of his pass-rushing ability.
The Verdict: The Falcons have several quality pieces and could probably field two defensive ends and three out of the four necessary linebackers to make the switch to a 3-4. The big question marks in my mind would be nose tackle and, depending on how guys like 'Spoon and Sidbury adapt to the system, outside linebacker.
If Nolan did decide to make the change, I think it's feasible. It would likely be a tough transition in one year, though.