A careful observer of the 2013 Seattle Seahawks will have noticed something about the team's fearsome defensive line: its fluidity.

(Here come the numbers. We're using regular-season stats. Straight from www.footballoutsiders.com's snap count page.)

Michael Bennett played exactly 600 defensive snaps for the Hawks last year. That led the team among D-linemen. But it placed him ninth among his position peers in the NFC West. And 79th among D-linemen overall. And 301st in the league in total defensive snaps taken.

Observation One: The Seahawks rotate quite a bit more than their immediate rivals, and the rest of the NFL, for that matter.

Witness the following anonymous table:

Arizona (3-4 base D) San Fran (3-4) St. Louis (4-3) Seattle (4-3) Total number of snaps played by each D-lineman 963, 865, 357, 285, 226, 77 780, 642, 435, 378, 302, 26, 18 839, 831, 792, 743, 385, 345, 212, 135, 10 600, 570, 551, 531, 530, 528, 481, 144, 84, 63, 46, 24, 15 Total number of snaps played by top 2 D-linemen 1828 1422 1670 1170 D-linemen with more than 400 snaps 2 3 4 7

Division rivals rely on established starters to carry the load, snap-wise. In Arizona, two guys each played 80 percent of the team's snaps; in San Francisco, it was two just linemen who appeared in 60 percent or more of the snaps, plus a job-share for the last DL spot; in St. Louis, there were four guys who logged 70 percent or more of the available playing time.

Meanwhile, in the CLink's cozy, cacophonous confines, no Seahawk lineman saw the field more than 60 percent of the time. Seven guys played between 46 and 57 percent of available defensive snaps. That's right, the leading snap-getter for Seattle only played four out of every seven snaps.

The numbers beg another table.

Arizona San Fran St. Louis Seattle Total D-linemen used in 2013 6 7 9 13 Snap gap between most used DL and top non-starter 678 402 454 70

Pete Carroll's defensive line rotation has effectively blurred the line between starter and backup.

Sure, both the the Cards and the Niners have a job-share going for their third DL spot. Sure, the Rams had a couple non-starters reach 300 snaps. But nobody in the fiercest division in football is doing things on their D-line quite like the Seahawks are.

In fact, almost nobody league-wide rotates like Seattle. Three facts:

1. New England has two D-linemen who played more than 1000 snaps each: Chandler Jones and Rob Ninkovich.

2. A whopping 17 teams placed three D-linemen ahead of Bennett in total snaps played; 11 teams placed four guys ahead of him.

3. Only one team's snaps leader came in under Bennett's 600: Denver's Terrance Knighton with 597. As it happens, only one team is comparably dedicated to rotating like the Seahawks... and that's the reigning AFC champions of the world.

Denver's snap list: Knighton 597, Jackson 591, Wolfe 553, Ayers 506, Vickerson 390, Unrein 354, Williams 297, and a couple scrubs. John Fox kept his men pretty fresh for the Super Bowl too. That's nice.

Observation Two: In Which The PCSeason Is Unveiled

It's easy to quickly grasp the benefits to resting D-linemen. Fresher pass rushers and run stuffers will perform better than their gassed counterparts, right? That's got to help once the fourth quarter rolls around.

Yeah, but I'd like to submit that Carroll is not thinking just about each game's final minutes. In an effort to keep his guys fresh in the...

short term (single games),

medium term (single seasons),

and long term (for a whole career),

...the Seahawks' head coach used 2013 to stealthily implement a thing I like to call the PCSeason. (Say it out loud, it's more fun that way.) This PCSeason is a unit of measurement that lasts 542 snaps.

542 is not a random number! Add up all of the snaps played by Bennett, Clemons, Avril, Mebane, McDonald, McDaniel and Bryant. It comes to 3791. Divide by 7. Round up. There's your 542. Under Pete Carroll, a regular season for an average starting Seattle D-Lineman lasts 542 snaps.

Seattle's seven guys all came in between 481 and 600 snaps, in fact. By design, they ended the year bunched up, practically interchangeable -- maybe not by role, but by size of role.

(Important side note: Brandon Mebane definitely wins if we shift to comparing size of roll.)

Well, If a PCSeason is 542 snaps, then how many PCSeasons of work did each NFCW lineman put in last year?

Lots.

Player Actual 2013 Snaps PCSeasons Played in 2013 Arizona 1 963 1.78 Arizona 2 865 1.60 STL 1 839 1.55 STL 2 831 1.53 STL 3 792 1.46 SF 1 780 1.44 STL 4 743 1.37 SF 2 642 1.18 Bennett 600 1.11 Clemons 570 1.05 Avril 551 1.02 Mebane 531 0.98 McDonald 530 0.98 McDaniel 528 0.97 Bryant 481 0.89

Look at all those Hawks hanging around the 1.00 mark.

As I throw the final table at you, it's time at last to lift the anonymity, so you can find out whose body will suffer the most for not being a Seahawk. Check out the same table with names and ages, except the snap number is now tripled. How many PCSeasons are each of these opponents theoretically on the hook for in 2013-14-15?

Of course, playing time changes, rosters turn over, starters become backups, yada yada yada. Campbell isn't necessarily going to play more than five PCSeasons in the space of three years; Justin Smith isn't necessarily going to play four and a third.

But old guys like Dockett and Long and Smith can't really afford to be playing more snaps than their rivals -- it's not like they have unlimited years ahead of them.

Then peek at the Rams' line. Full of young bodies like Robert Quinn and Michael Brockers. Good for them, right? Until those guys play an extra PCSeason and a half. Then what happens to their age advantage?

Meanwhile, the Hawks rest. What Pete Carroll is doing here is nothing short of genius, in my opinion. So:

Observation Three And Also Conclusion: Pete Carroll is smarter than me/us.

Duh.

In addition to not wearing his players out, Carroll is likely mitigating the effect of injuries on two fronts.

1. A deep rotation inoculates the team against one single injury. Losing 500 snaps to a season-ending surgery is not the same as losing 800.

2. Each Seahawk is less likely to get injured in any given season than his divisional counterpart who's logging 800-plus snaps.

Injuries will happen. The Hawks are playing almost as many snaps as their competition, after all. Guys missed time last year and they will again this year.

But it sure seems like Carroll's rationale for rotating his armada of linemen stretches beyond the scope of a single game, or a single season even. In an age governed by what-have-done-for-me-lately-ness, and constant urgency, where job insecurity can compel coaches to rely more and more on just their stars, it's more like Carroll is aiming to win now AND later. Somebody get that man a slogan!