by Scott Kacsmar

With the free-agency ink dry and the draft quickly approaching, we are deep into the team-building part of the football year. Teams are planning around the salary cap, getting younger and making moves for the future.

What is the right mixture of youth and experience for an NFL team to be successful?

This is a question we are not able to definitively answer, but age is just a number, so we can quantify it. Football Outsiders uses a metric called Snap-Weighted Age (SWA) that's designed to depict a team's average age based on snap counts. Some of the oldest players in the league are usually on special teams, but since they play a limited number of snaps, that should be factored into the calculation. Every player's age is weighted by how many regular-season snaps they played.

Going back to that question of a right mixture of age, 2014 did not provide much help. The correlation between a team's SWA and DVOA was -0.03. In recent seasons we observed a correlation slightly above 0.30 between offensive SWA and offensive DVOA. Last season was just 0.12, lower than defense (0.19). The league-wide SWA for defense was 26.7, same as 2013. Offense dropped a tick from 27.0 to 26.9 thanks in part to an incredible class of rookie wide receivers.

The answer may simply be that there is no superior way of building a team. While 2014's three oldest teams (Saints, Bears and Chargers) all missed the playoffs, the league's third-youngest team was one yard away from back-to-back championships. Old or young, drafted or a free agent, good players with good coaching is what drives success in the NFL. Teams have to explore every avenue to maximize the number of good players on their roster. That's always the goal.

In presenting SWA, we try to withhold any comments on whether a team's ranking is good or bad. Their methods of arriving at that ranking matter much more. If a team has a great defense with a lot of veterans, who are we to criticize them? That just may be a signal that this team needs to start investing into the future on that side of the ball.

Nothing lasts forever.

Snap-Weighted Ages for 2014

The following table shows SWA for the overall team (TOT) along with the unit breakdown for offense, defense and special teams. Teams are ranked from oldest to youngest.

Team TOT Age Rank OFF Age Rank DEF Age Rank ST Age Rank ARI 27.1 4 27.3 10 27.1 9 26.4 5 ATL 26.6 20 26.8 16 26.6 21 26.4 7 BAL 26.8 17 27.4 8 26.8 15 25.4 31 BUF 26.3 26 26.6 21 26.1 26 26.1 15 CAR 26.7 19 26.4 26 27.2 8 26.4 6 CHI 27.2 2 27.9 3 27.0 12 26.3 9 CIN 26.9 16 25.9 29 28.1 2 26.1 14 CLE 26.4 25 26.6 18 26.4 22 25.8 23 DAL 26.1 29 26.4 25 26.1 25 25.6 29 DEN 26.9 15 28.6 2 25.7 31 25.6 27 DET 27.0 7 27.0 15 27.5 6 25.9 20 GB 26.2 28 25.7 30 26.7 18 25.9 19 HOU 26.5 22 27.2 12 26.0 28 26.1 17 IND 27.0 8 26.2 28 28.3 1 26.1 12 JAC 25.4 32 24.7 32 26.1 27 25.5 30 KC 26.4 24 26.6 19 26.6 20 25.7 26 Team TOT Age Rank OFF Age Rank DEF Age Rank ST Age Rank MIA 26.6 21 26.2 27 27.3 7 25.7 25 MIN 26.2 27 26.7 17 25.9 29 25.6 28 NE 27.0 10 27.7 5 26.6 19 26.1 16 NO 27.3 1 29.0 1 26.2 24 25.9 22 NYG 27.0 11 26.6 20 27.6 5 26.7 3 NYJ 27.0 9 27.3 9 27.0 11 26.1 13 OAK 26.9 14 26.5 22 27.7 4 26.2 11 PHI 27.0 6 27.2 11 26.9 13 26.9 1 PIT 26.9 13 26.5 24 27.8 3 26.2 10 SD 27.2 3 27.9 4 26.7 17 26.6 4 SEA 25.8 30 25.3 31 26.3 23 25.8 24 SF 27.1 5 27.6 6 26.8 16 26.4 8 STL 25.6 31 26.5 23 25.0 32 25.2 32 TB 26.5 23 27.5 7 25.7 30 26.0 18 TEN 27.0 12 27.0 14 27.0 10 26.7 2 WAS 26.8 18 27.1 13 26.9 14 25.9 21 AVG 26.7 26.9 26.7 26.0

How did the Broncos finish with the second-youngest defense? DeMarcus Ware (32) was the only player older than 28 to play any snaps. Denver also had the second-oldest offense, giving the Broncos the biggest age differential in the league between its offense and defense.

Saints: Can They March Out of Cap Hell?

New Orleans was the oldest team in the league last year thanks to the game's oldest offense. Sure, it has been a historic offense since Sean Payton met Drew Brees, but things slipped a little and a case of cap hell is threatening to drop the offense deeper in 2015.

The Saints traded Jimmy Graham in a blockbuster move to Seattle, which might mean more snaps for 35-year-old Ben Watson. That's probably going to have to be fixed in the draft. Pro Bowl center Max Unger was also part of that deal, which makes the Saints seven years younger at center after 14 starts from the departed Jonathan Goodwin (36) last year. The Saints also said goodbye to "screen legend" Pierre Thomas (30) and traded Ben Grubbs (31) to Kansas City.

So the team has dumped some veteran contracts, though they also traded 23-year-old receiver Kenny Stills to Miami. The core trio of Saints that has paced this offense since 2006 (Brees, Jahri Evans and Marques Colston) remains, but the Saints are going to look a bit different in 2015.

Steelers: Still Old, But Not the Oldest Defense

Arguably the craziest SWA stat we've had so far is that Pittsburgh had the oldest defense for seven consecutive seasons (2007-2013). That streak is over after the Colts and Bengals edged out third-place Pittsburgh in 2014. We thought the Steelers would be even younger, but Cortez Allen's benching and injury-plagued seasons for Jarvis Jones and Ryan Shazier nixed that. The team even brought James Harrison and Brett Keisel back, but only the 37-year-old Harrison should return for 2015. Troy Polamalu and Ike Taylor recently retired after 12-year careers in Pittsburgh, so a revamped secondary should lead the team to its youngest defense under Mike Tomlin.

With defensive coordinator Dick LeBeau also gone, this really is the end of an era in Pittsburgh, at least for the defense. We may never see a streak in SWA like this again, because this was certainly done by design. Since Kevin Colbert took over as general manager in 2000, no team has been able to find and keep as many defensive stalwarts as the Steelers. Since 2000, the Steelers have had eight defenders play at least 150 regular-season games for them. The rest of the NFL has had just 21 such defenders in that time.

Re-checked and Lance Briggs was the only omission from the first table. So it's 29 total players. pic.twitter.com/oratYNL5Xw — Scott Kacsmar (@FO_ScottKacsmar) April 14, 2015

Colts: Drafting Andrew Luck Was Ryan Grigson's "Easy Button"

Yes, that was a Staples reference. Indianapolis' path to becoming the oldest defense is the complete opposite of what the Steelers did. The Colts got there due to not finding players in the draft and having to load up the roster with veteran free agents and trades. Only 15.3 percent of Indianapolis' defensive snaps last year were from players the Colts drafted. By comparison, a team like Oakland gets to 16.7 percent on just Khalil Mack and Miles Burris alone. If we include undrafted free agents that only the Colts have had, that number is still just 27.5 percent.

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The Colts finished with the oldest defense despite the unit's best player, a 33-year-old Robert Mathis, missing the entire season due to suspension and injury. Their top three players in defensive snaps are all coming back in 2015 and will be at least 30 years old: Mike Adams (34), D'Qwell Jackson (32) and Greg Toler (30). This offseason the Colts added pass rusher Trent Coles (33) and safety Dwight Lowery (29), though their roles are to be determined.

Ryan Grigson has drafted one defender (Bjoern Werner) in the first four rounds of the 2012-14 drafts compared to eight offensive players. If Grigson does not start finding defenders, the Colts will continue spending on other team's players and filling out the roster with undrafted talent.

Only the Bengals had a roster with a larger age differential in favor of defense than the Colts. That could be changing this season with the Colts adding Frank Gore (32) and Andre Johnson (34) on offense, though we are still talking about short-term fixes. The lack of young building blocks on defense is a major problem.

Given what Grigson has built with Andrew Luck making a comparatively meager quarterback salary, it's scary to think what the team might look like when Luck is the highest-paid player in NFL history.

Growing Older, Growing Up?

If we compare SWA from 2014 to 2013, we can see which teams aged the most or went into the biggest youth revolt.

The Jets ranked 27th in offensive DVOA in 2013, but Geno Smith was only a rookie. He started 13 games last year and the Jets added Eric Decker, Jace Amaro, Chris Johnson and eventually traded for Percy Harvin. The Jets again ranked 27th in offensive DVOA while gaining a league-high 1.1 SWA (only team above 0.7).

Jacksonville went in the other direction. After ranking 32nd in offensive DVOA, the team dumped Maurice Jones-Drew for younger running backs, drafted Blake Bortles and surrounded him with three young receivers (Marqise Lee, Allen Robinson and Allen Hurns). The offensive line also started multiple rookies, leading to a league-high decrease of 1.9 in SWA. The end result was a ranking of 31st in DVOA (32nd in passing). The offense helped make the Jaguars the youngest team in the league, and adding a 27-year-old Julius Thomas should only help maintain that. Marcedes Lewis (31) hadn't shined since the 2010 season. We have SWA data back to 2006 and the Jaguars are the youngest offense (24.7) on record.

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Switching to defense, the Vikings had the biggest youth movement (-1.2 SWA) last year, saying goodbye to Jared Allen (32) and hello to rookie Anthony Barr. Cornerback Xavier Rhodes also became a 16-game starter in his second year. Mike Zimmer figured he could turn a young defense around in his first year, though the Vikings only climbed from 27th in defensive DVOA to 23rd in 2014. It is however a process and the Vikings should be moving in the right direction with players like Barr, Rhodes and Sharrif Floyd.

Cleveland gained the most experience on defense (+0.9 SWA) thanks in part to players like Karlos Dansby (33) and Donte Whitner (29; made the Pro Bowl). While Mike Pettine's defense struggled early, by season's end the Browns improved from 24th to 11th in DVOA (eighth in weighted DVOA) and will have to carry the team in 2015.

Again, it's not necessarily good or bad make these types of changes. Sometimes "aging" is just a roster sticking with a working core, and we know everyone only ages in one direction. One year after the San Diego defense had the biggest SWA decline (-1.9), the Chargers had the second-largest rise in SWA (+0.9) this season. They let those players grow together.

The Washington Tradition Ends

We have not forgotten special teams. The strongest correlation for SWA to DVOA in 2013 was on special teams. It was also negative (-0.35), but that correlation also shrunk close to zero in 2014 (-0.07).

Chip Kelly's Eagles had the oldest special teams, but finished first overall in special teams DVOA. Kelly's squad only ranked 25th in 2013 when the unit ranked 19th in SWA. I wouldn't say he has this down to a science yet.

For eight years in a row (2006-2013) the Redskins ranked among the four oldest special teams in the league. That finally changed in Jay Gruden's first year with a ranking of 21st, though some credit probably belongs to new special teams coordinator Ben Kotwica, an Iraq war vet. This story by Mike Jones of the Washington Post summarizes some of Kotwica's methods to get guys motivated for his "special forces." It also touches on some of the craziness during that abysmal 2013 performance, including ex-coordinator Keith Burns challenging a player to fight him.

Despite the efforts to get younger in Washington, the special teams still ranked 29th in DVOA with a negative rating in each of the five elements we measure. Just goes to show you can change the culture, but you can't magically will Kai Forbath to kick more touchbacks.