Last August, I looked at the 2011 age-adjusted team rosters. I have reproduced the intro to that post below:

Measuring team age in the N.F.L. is tricky. Calculating the average age of a 53-man roster is misleading because the age of a team’s starters is much more relevant than the age of a team’s reserves. The average age of a team’s starting lineup isn’t perfect, either. The age of the quarterback and key offensive and defensive players should count for more than the age of a less relevant starter. Ideally, you would want to calculate a team’s average age by placing greater weight on the team’s most relevant players.

Using Pro-Football-Reference’s Approximate Value system, I calculated the weighted age of every team in 2012, with the weight for each player being proportionate to his contribution (as measured by AV) to his team. You don’t have to use AV — Danny Tuccitto did an excellent job producing age-adjusted team rosters based on the number of snaps each player saw — but since AV is what I’ve got, AV is what I’ll use.

The table below shows the total AV for each team in 2012. The table is sorted by the team’s average (AV-adjusted) age. I’ve also included the offensive and defensive AV scores and average ages for each team.

Seattle is in fantastic shape

The Seahawks rank as the youngest team in the league thanks to the 3rd youngest defense and the 4th youngest offense. And that’s before they added Percy Harvin, who doesn’t turn 25 until May. Cliff Avril and Michael Bennett are in the primes of their careers, and will actually lower the defense’s age if they replace Chris Clemons. Richard Sherman, Earl Thomas, Bobby Wagner, Bruce Irvin, Kam Chancellor, and K.J. Wright were all under 25 last year, a scary thought for NFC West offenses. Only one of the 11 offensive starters was older than 27 last year (29-year-old left guard Paul McQuistan), so the Seahawks are in excellent shape on that side of the ball, too.

Offenses

Cincinnati had the youngest offense in the NFL last year, as Andy Dalton and A.J. Green are surrounded by other young talents like TE Jermaine Gresham and WR Andrew Hawkins. In addition, four of the five starters on the offensive line were 25 or younger last year, so the team is in good shape there as well. BenJarvus Green-Ellis turns 28 in July, but the Bengals have the pieces in place to make strides on offense as they come closer to reaching their potential in 2013.

On the other side, San Diego is in the rare position of having both an old and unproductive offense. Philip Rivers, Nick Hardwick, and Antonio Gates were young Pro Bowlers in 2006, but seven years later, they still form the base of the Chargers offense. Rivers, Hardwick, and Malcom Floyd will be 32 in 2013, while Gates turns 33 in June. It doesn’t help that one of the few young players on offense, guard Louis Vasquez, signed with rival Denver last week.

Defenses

You probably don’t think of the Titans as a young defense; well, you probably just don’t think about the Titans defense at all. Tennessee allowed the most points in the league last year and ranked 30th in first downs allowed. One possible reason for that: four of the last five first round picks (Kendall Wright, Jake Locker, Kenny Britt, and Chris Johnson) were used on offense, but the Titans have found a lot of defensive starters — for better or worse — later in the draft. The one first round pick used in defense was used to grab Derrick Morgan in 2010, and Morgan had a breakout season last year. Since 2009, the Titans have used second round picks on three starters (DT SenDerrick Marks and LBs Akeem Ayers and Zach Brown), a third rounder on DT Jurrell Casey, and picked up three more starters in the later rounds (MLB Colin McCarthy, CB Jason McCourty, and CB Alterraun Verner). The defensive line should be in good shape for years: in addition to 2012 third round pick Mike Martin, who played well as a rookie, the Titans bolstered the team’s depth by signing Sammie Lee Hill from Detroit. Older players like Kamerion Wimbley, Will Witherspoon and Michael Griffin were weak links on the defense, so there’s actually reason for some optimism going forward in Nashville. If nothing else, Titans fans can rest easy knowing that there will be a wise guru showing the young defense the light in 2013.

As for the oldest defense… well, it’s getting old talking about how old Pittsburgh’s defense is. This is what I wrote THREE years ago, when the Steelers’ defense had an average age of 29.2:

The Pittsburgh Steelers fielded the oldest defense in the N.F.L. last season, with graybeards across the defensive line in Travis Kirschke (35), Aaron Smith (33) Casey Hampton (32) and Brett Keisel (31). The back eight wasn’t much younger, with linebackers James Farrior (34) and James Harrison (31) playing in front of safeties Tyrone Carter (33) and Ryan Clark (30). Pittsburgh gets Troy Polamalu back in the secondary to replace Tyrone Carter, but he’s already 29. On draft day, the Steelers reacquired cornerback Bryant McFadden (28) to provide an upgrade over CB William Gay (24), but that won’t make the lineup younger. Last year’s first-round pick, Ziggy Hood, should start at defensive end, but Pittsburgh will once again field one of the oldest defenses in the league in 2010.

You can understand why the Steelers haven’t addressed the age of the defense much in the off-season: two years ago, the same unit was an absurdly dominant group that led the team to a Super Bowl title. Pittsburgh will try to eke out one more run with Smith, Hampton, Farrior, Harrison and Polamalu.

I don’t think I wrote about how old Pittsburgh’s defense was after the 2010 season, but here’s what I wrote in my 2012 preview, after noting that the average age of the 2011 defense was 29.5:

After one week, Warren Sapp loudly declared that Pittsburgh’s defense was old and slow, and that it was over for the modern Steel Curtain. As it turned out, he was only right about one thing: Pittsburgh was very old last year. In 2009, 2010, and 2011, Pittsburgh’s starting linebackers were James Harrison and LaMarr Woodley on the outside, with James Farrior and Lawrence Timmons on the inside. Farrior retired in the off-season, but will be replaced by Larry Foote. Foote (32) and Harrison (34), are on the wrong side of 30, but the other two Pittsburgh linebackers are in the primes of their careers.

The bigger concern may be in the secondary. Cornerback Ike Taylor (32 in 2012) and safeties Troy Polamalu (31) and Ryan Clark (33) have seemingly been Steelers forever, and the secondary is never where you want to be old. On the defensive line, Brett Keisel turns 34 and Casey Hampton 35 this year, with the latter coming off knee surgery and currently on the physically-unable-to-perform list. There’s no getting around it: Pittsburgh’s defense was old last year, and will be old this year. Incredibly, six of the defensive starters on the 2006 team are projected starters for the 2012 Steelers. But Pittsburgh ranked 1st in both points and yards allowed last season, so even a small dropoff may not mean much. And let’s not forget, in addition to Timmons and Harrison, Pittsburgh has youth in the front seven with Cameron Heyward, Jason Worilds, and Evander Hood, and some young but untested players in the secondary.

Well in 2012, the average age of the defense was 29.7, even old by ancient Steelers standards. Larry Foote (32) and James Harrison (34) were still starting linebackers last year, although Harrison won’t be back in 2013. When Polamalu was injured, which was most of the time, 30-year-old Will Allen took his spot at safety. And Brett Keisel (34 in 2012) and Casey Hampton (35) — still — remain on the line (for some perspective, Hampton was a teammate of Ricky Williams in Texas. The one bright spot is that DE Cameron Heyward came on at the end of the season, so he could see more playing time in 2013.

For awhile, the big concern on the Pittsburgh defense was age. Now the real question — despite the defense getting older — is talent. The defensive line needs Hood and the other young players to improve, the secondary could be an issue even with a healthy Polamalu, and there’s still no one to replace Harrison as a pass rusher. Fortunately for Pittsburgh, Dick LeBeau has managed to field a strong defense nearly every season, and he might be able to get one more year out of the current group. Even in 2012, the Steelers led the league in yards and first downs allowed and ranked second in Net Yards per Attempt Allowed. And, of course, Pittsburgh can take some solace in the fact that it hasn’t exactly been the best off-season in Baltimore.