Closer look: Defensive starter projections

We interrupt ongoing coverage of Michael Crabtree's surgically repaired Achilles tendon to continue our recent discussion on average ages for projected 2013 NFL starting lineups.

Offense went first. Defense is up next.

2013 Starter Age Rankings (Defense)

The chart ranks teams by average ages for defensive starters.

I've recalculated the numbers and you can see just how close some of them are -- indistinguishable, in some cases. One change to the projected starting lineup could affect the order by several places.

The way the ages are calculated -- number of days since birth divided by 365.25 to account for leap years, then rounded down to the tenth of a year and averaged -- can cause slight changes to the order from one day to the next. That happened with the defenses for New England and Baltimore over the past couple days, for example. They actually switched places from a couple days back because the calculation for Tommy Kelly's age changed from 32.3 to 32.4.

For that reason, I'm more interested in the extremes from one end of the rankings to the next. A few spots here or there? No big deal.

The gradual changes add up through the range of teams, and we can see why the Chicago Bears weren't all that excited about bringing back Brian Urlacher to a defense that has the oldest starting linebackers without him.

A few thoughts on the defensive numbers for NFC West teams:

  • Arizona Cardinals: Arizona released veteran safeties Adrian Wilson and Kerry Rhodes primarily to shed their contracts. Had getting younger been the priority, Arizona wouldn't have signed 35-year-old Yeremiah Bell as a replacement. His presence on the roster pushes up the average age in the secondary. Parting with Paris Lenon, 35, made the Cardinals younger at linebacker. This team had too many older backups in the past, I thought. That is changing. Note that the Cardinals had the NFL's third-oldest starting defense entering the 2010 season. That group averaged 29.3 years old. The current one averages 27.8 even with Karlos Dansby projecting as a starter over Kevin Minter. I listed Dansby and Daryl Washington as the starters at inside linebacker despite the four-game suspension Washington must serve to open the season.

  • San Francisco 49ers: The 49ers had the NFL's oldest starting defensive line last season. That will not be the case in 2013 now that Isaac Sopoaga left in free agency. Replacing Sopoaga and free safety Dashon Goldson with younger players has brought down the 49ers' average age across the defensive lineup. And if the draft secured an eventual successor for 33-year-old Justin Smith, the 49ers should be set up on defense for years to come. Note that strong safety Donte Whitner is entering his eighth season, but he won't turn 28 until July.

  • St. Louis Rams: The Rams own the second-youngest projected starting defense in the NFL. Their starting defensive backs, defensive linemen and linebackers all rank among the NFL's five youngest at their position groups. That is much younger than the Rams were on defense a few years ago. The biggest question initially is whether the Rams' young safeties, including rookie third-round draft choice T.J. McDonald, are ready to play prominent roles. Signing a veteran safety for insurance could make some sense, but this is looking like a season when youth will be served throughout nearly all the Rams' roster, save for portions of the offensive line. There's much to like about a young defensive front featuring Michael Brockers, Robert Quinn and veteran Chris Long.

  • Seattle Seahawks: There was some projecting at work in putting together a lineup for Seattle. I plugged in Malcolm Smith at linebacker and went with a defensive line featuring Red Bryant, Tony McDaniel, Brandon Mebane and Cliff Avril. That line would hardly be ancient, but it would rank among the older third of projected starting lines. Bruce Irvin's suspension and Chris Clemons' knee injury limit the options. We could see rookie Jesse Williams at defensive tackle over McDaniel, who has mostly been a rotation player. The Seahawks would have the youngest projected starting linebackers in the league if Smith joined Bobby Wagner and K.J. Wright in the lineup. The starting secondary ranks seventh youngest. However, nickel corner Antoine Winfield is 35 years old and could wind up playing half the snaps, or more.