But for which team?
There will be a handful of clubs with a head coaching vacancy when 2014 begins, so let's identify the best fits for the former Chicago Bears coach from a defensive personnel perspective.
Here's a look at how the Titans would look on defense compared to the famed, NFC-winning Bears defense of 2006, via Pro Football Reference:
The Titans have quite the collection of personnel exquisitely suited to run a successful 4-3 defense.
Beginning on the line, Jurrell Casey and Karl Klug might be the preeminent one-gap 4-3 defensive tackle duo in the NFL with the brightest future, as Casey's only 24 and Klug a few months away from being 26.
In 4-3 defenses, the linemen only have the "responsibility" to "cover" one gap, which allows them to frequently penetrate upfield; therefore, quicker, more agile, pass-rushing defensive tackles are needed.
Per Pro Football Focus (subscription required), Casey has played 443 pass-rush snaps and has forced 52 quarterback pressures (sacks, hits or hurries)—the third-most at his position.
Klug isn't far behind, either.
He's been credited with 20 quarterback pressures on a mere 184 pass-rush snaps in 2013.
At the end spot, Derrick Morgan only has four sacks on the year, but he has 48 pressures in 397 pass-rush snaps heading in to Week 16.
At 6'2'' and 254 pounds, Akeem Ayers is the epitome of a 4-3 strong-side linebacker. He sets the edge well, is the best blitzing linebacker on the roster and, if needed, he can drop into coverage without being a major liability. The former UCLA star will be only 25 in July.
Colin McCarthy isn't the next Brian Urlacher, but he's more of a sideline-to-sideline middle linebacker than he is a downhill thumper, which is fine in the 4-3 defense.
Zach Brown, the team's 2012 second-round pick out of North Carolina, exudes athleticism at the weak-side linebacker position. With more experience should come more polish, something he needs.
On the outside, Jason McCourty and Alterraun Verner formulate the stingiest cornerback tandem no one talks about.
Per PFF, Verner has allowed the third-lowest catch percentage among cornerbacks who've taken at least 25 percent of their respective team's snaps in 2013 (47.2).
McCourty isn't far behind at 60.5.
Michael Griffin is one of the more underappreciated safeties in the NFL, and although George Wilson and Bernard Pollard have been decent stand-ins this season, Tennessee would probably like to get younger at that position.
However, the youthful talent in the front seven and the sound cornerback play could make the Titans a dream job for Smith, especially from a defensive perspective.
Let's plug the Lions defenders into the 2006 Bears alignment:
Outside of the Seattle Seahawks, the Detroit Lions have the most dangerous defensive line in the NFC. The defensive tackle pairing of Ndamukong Suh and Nick Fairley is dynamite, particularly when the two are attacking the quarterback up the middle.
According to PFF, Suh has forced 64 pressures on 469 pass-rush snaps this season. Fairley has forced 33 on 348.
If Smith wants two stud defensive tackles to create havoc on the interior, he'll get that in Detroit.
On the outside, relatively raw rookie Ezekiel Ansah has racked up eight sacks in 2013 and looks to have an extremely bright future as a 4-3 defensive end.
The long and lean Devin Taylor, another rookie, has shown flashes this season as well. The most unheralded member of the Lions defensive front is Willie Young, a 2010 seventh-round choice out of North Carolina State.
He's much more stout against the run than he is terrorizing rushing the passer, but Smith would love what Young brings to the field.
Detroit's linebacking corps could use some young legs, but Stephen Tulloch and DeAndre Levy have settled into their respective middle and weak-side positions this season—both excel in coverage.
There's work to be done in the secondary, however.
Rashean Mathis is in the twilight of his career, and Chris Houston has struggled mightily. Darius Slay, the Lions' second-round pick in 2013, has shown some glimpses of his potential, but more cornerback help is definitely needed.
At safety, the combo of Glover Quin and Louis Delmas would be good enough for Smith's liking.
Suh, Fairley, Ansah, Tulloch and Levy would be an enticing quartet for any coach to inherit.
Tampa Bay Buccaneers
Here's how the Buccaneers lineup compares to the 2006 Bears:
The Buccaneers have a wealth of talent on defense. It's frightening, actually. For a head coach with deep 4-3 roots, Tampa Bay's defensive personnel couldn't be much more appealing.
Starting up front, former No. 3 overall pick Gerald McCoy has morphed into, arguably, the best one-gap defensive tackle in the game during the 2013 season.
Per Pro Football Focus (subscription required), on 506 pass-rush snaps heading into Week 16, McCoy has 75 quarterback pressures—the most among all defensive tackles in the NFL.
He's the ideal anchor of a 4-3 defense.
Adrian Clayborn could be kicked inside to play alongside McCoy, where the former Iowa standout would almost assuredly see many one-on-one situations.
At linebacker, Mason Foster is serviceable in the middle, although Smith may want a "Mike" who's a bit more fluid getting down the seam in coverage.
Next to Foster is Lavonte David, the prototypical 4-3 weak-side linebacker.
Playing in a flashy, "clean up" role, David "flashes" often.
The former second-round pick out of Nebraska flies around the field, has demonstrated quick-twitch athleticism and lightning-fast reaction.
He blitzes well, sifts through traffic against the run and is a smooth cover guy.
With David, think a faster, younger and spryer version of Lance Briggs.
Outside sits the one and only Darrelle Revis. While Smith's system is predicated on an abundance of Cover 2 zone, the scheme could easily be tweaked to allow Revis to play press man on most occasions. Having the ability to erase the opposition's No. 1 wideout is the ultimate luxury for a defensive coordinator.
Just ask Rex Ryan.
The Buccaneers could use a few more traditional 4-3 defensive ends, bigger pass-rushers who aren't liabilities against the run and who don't need to drop into coverage, but rookie William Gholston has come along nicely in the late stages of 2013.
At safety, Dashon Goldson and Mark Barron have their moments, yet a team could do much worse on the back end.
Oh, and Smith was linebackers coach in Tampa Bay from 1996 to 2000.
Easily, the best fit for the former Bears coach to run his 4-3 defense is with the Buccaneers.