Background:

• 2012 AV
• 2013 AV
• 2014 AV
• 2015 AV

I thought it would be fun to do a quick checkdown and look at the AV-Adjusted team age for each defenses over the last four years. Here’s how to read the table below, using the Bears as an example. In 2012, Chicago’s average age on defense was 29; in 2013, it was 27.7, then 27.5, and finally, 26.1 last season. That means the Bears average age has had a variance of 1.1 years, the second largest in the data set behind only San Diego.

Given how the Bears average age has consistently declined, and the fall-off from a top unit in 2012 to garbage the last 3 years, I thought it would be more interesting to examine Chicago’s defensive changes than San Diego’s. In 2012, Chicago ranked 1st in DVOA; that rank has been 25th, 28th, and finally, 31st last year. So the defense has gone from great to bad, really bad, and really, really bad.

In 2012, Chicago had five defenders with double digit AV grades that were 29 or older: Julius Peppers (age 32, AV of 18), Charles Tillman (31, 16), Tim Jennings (29, 13), and Lance Briggs (32, 11). Add in Israel Idonije (32, 8) and Brian Urlacher (34, 8), and over half of Chicago’s starting defense was on the wrong side of the age curve. In retrospect, it’s not surprising that this was the last great Bears defense.

In 2013, Jennings (30, 8), Peppers (33, 7), Briggs (33, 4), and Tillman (32, 3) were still around, but were much less effective. And the “young replacements” were guys like Chris Conte, Corey Wootten, Major Wright, Shea McClellin, Stephen Paea, and Jonathan Bostic; none of those players are still on the team, so that’s a sign of how Chicago was unable to rebuild and reload on the fly.

In 2014, Jared Allen (32, 6) was actually tied for the team lead in AV with Paea (26); Chicago also had veterans like Jennings (31), Ryan Mundy (29), and Jay Ratliff (33) around, not to mention eight final games from Briggs. But the youth movement from ’13 was still in effect, and Peppers and Tillman were gone, while rookie Kyle Fuller started 14 games.

Finally, last season, Chicago had eight players start ten games, and none of them were 30: that includes Adrian Amos (22), Fuller (23), Jarvis Jenkins (27), Christian Jones (24), Tracy Porter (29), Eddie Goldman (21), Pernell McPhee (27), and McClellin.

Here’s another way to think about the Bears turnover on defense. Over the last four seasons — i.e., 64 games — only three players have started at least 34 games: Jennings (46), Conte (43), and Paea (40). And none of those players were on the roster last year! Over the last three years, no player has started 33 games: the leaders are Jennings (32), McClellin (31), Fuller (30), Conte (28), and Paea (26). No other player is at over 20 games started over the last 48 Bears games, and as 2016, Jennings is a free agent, McClellin is a Patriot, Conte is a Buccaneer, and Paea is in Washington. That leaves Fuller as the only player to start in at least 20 games for Chicago over the last three seasons and to still be on the 2016 roster.