2012 Total by Roster Status
Roster change can be good for teams looking to dramatically upgrade.
The Arizona Cardinals, for instance, have parted with players who logged 8,842 offensive and defensive snaps last season, or 39.1 percent of the total, according to ESPN Stats & Information.
The figures are 36.3 percent for the St. Louis Rams, 15 percent for the San Francisco 49ers and 10.6 percent for the Seattle Seahawks.
Those changes, displayed in the first chart, can help us frame in our minds how much these teams expect to change for the upcoming season.
Not all snaps carry the same value, of course. The Cardinals can reasonably expect the new snaps they get from quarterback Carson Palmer to help them more than, say, the new snaps they get from veteran safety Yeremiah Bell.
2012 Offensive Snaps by Roster Status
The 49ers and Seahawks were very good on both sides of the ball when last season finished. They were further along in their development than the Cardinals or Rams. They're hoping to stay the course, for the most part. And so it's natural they would return a higher number of key contributors from last season.
The second and third charts break down the numbers specifically for offense and defense.
We see the Rams in particular will be looking for change on offense. Robert Turner, Barry Richardson, Brandon Gibson, Steven Jackson, Danny Amendola, Matthew Mulligan, Wayne Hunter and Quinn Ojinnaka are among the players no longer on the St. Louis roster after playing at least 300 offensive snaps last season.
Newcomers Jake Long, Jared Cook, Barrett Jones, Tavon Austin, Stedman Bailey, Brian Quick, Chris Givens and Zac Stacy will be getting some of their snaps in 2013.
The Cardinals have also turned over quite a bit of their offense. Adam Snyder, D'Anthony Batiste, Early Doucet, Kevin Kolb, LaRod Stephens-Howling, John Skelton, Rich Ohrnberger, Beanie Wells, Pat McQuistan and Todd Heap are among the regular contributors (or projected contributors) from 2012 no longer with the team.
2012 Defensive Snaps by Roster Status
The final chart shows Arizona turning over a somewhat surprising 44.6 percent of its snaps on defense after a mostly successful season on that side of the ball.
Kerry Rhodes, Paris Lenon, William Gay and Adrian Wilson are all gone after playing at least 800 snaps last season. Quentin Groves, Greg Toler, Nick Eason, Vonnie Holliday and James Sanders are gone after playing smaller roles.
Some of these players were ones the Cardinals thought they could replace without declining. They'll be looking for upgrades in some cases.
Third-round choice Tyrann Mathieu will fill some of the void in the secondary. Second-round pick Kevin Minter steps in at middle linebacker, where Lenon had been a regular.
Note: I updated this item to reflect Ryan Lindley's status on the Cardinals' roster. Thanks, @cblack315.