Among starting positions where the Seattle Seahawks are potentially weakest in 2016, offensive line gets the most juice. Probably deservedly so, given that unit’s struggles last year coupled with the losses of Russell Okung and J.R. Sweezy in the offseason. But whereas those problems and defections may not be entirely resolved by the introduction of rookies and lower-tier free agents, at least we can see where the team took movements toward a solution (however worrying the outlook). The Seahawks likewise applied draft resources to the interior defensive gap left open by Brandon Mebane’s departure.

So I say the most compelling vulnerability is at strongside linebacker, the so-called SAM spot vacated when Bruce Irvin signed with the Oakland Raiders. It’s the only position that Seattle lost its starter and didn’t otherwise make some material investment to replace him or already have a clear successor for the role. I find it compelling not just for the mystery of the competition it leaves, though that should be fierce and fascinating, but because of what it suggests about the coaches’ changing value of the position and a possibility for dynamic new schemes.

Right now the main guys in the mix are sixth-year special teams ace Mike Morgan and two 2014 draft picks: former down lineman Cassius Marsh and onetime cornerback experiment Eric Pinkins. These veterans don’t so much have different levels of ability as different traits that make each a contender. If they could all play at the same time it would be awesome, but that would mean a lot of penalties for 13 men on the field. Frank Clark dispelled rumors he was in line to inherit the job, confirmed by OTA reports that he wasn’t practicing with the group. Clark emphasized he lost weight to speed his rush, not aid in coverage, and the team changed his listed designation back to DE (although Marsh is also still listed at DE, so read that how you want). There are also some undrafted rookies getting looks and Kevin Pierre-Louis has been in consideration, but weakside starter K.J. Wright wanted no part in it—even though Wright performed quite a lot at SAM before Irvin’s arrival.

Who climbs the ladder during training camp to seize this starting role? Rather than guess which player distances himself with his performance next month, let’s try to figure out what the Seahawks might be looking for at the position.

The confounding part about how little priority Seattle gave the spot is that it did so so soon after seeming to make a special investment by sliding the former first-round pick there three years ago. It’s one thing to decline paying premier pass-rusher money to a 4-3 outside linebacker, but in 2013 the Seahawks treated the position as important enough to reassign the 15th overall draft pick hot off an eight-sack debut season. Yes, it’s true they had just acquired Michael Bennett and Cliff Avril to rush the quarterback, but at the time that was more like reinforcement while Chris Clemons recovered from his torn ACL. Anyway, Avril and Bennett are still here and it doesn’t prevent Clark from getting his presumed shot at defensive end.

(Pause to reflect that a possible front four now includes Clark, Bennett, Avril AND Clemons.

@oracle gif me Homer Simpson drooling

Ummmmmm. Close enough.)

Remember, Irvin was the last player Seattle drafted in a first round until Germain Ifedi. Those kinds of low-cost/high-value pieces are some of the scarcer and more significant resources for any front office, and Irvin appeared especially prized by the organization because of the way they "reached" for him. Irvin playing SAM made it seem like a pivotal role. If the defensive coaches are so relaxed about who plays SAM now, why didn’t they just let Irvin rush the passer all along like he wanted?

The answer might have something to do with the changing faces of those coaches. Irvin’s shift to linebacker coincided with Dan Quinn’s appointment as defensive coordinator and a move back to a 4-3 "Under" front from the "Over" alignment that had become more prominent during the last few years of Gus Bradley’s defensive regime. The Under style required an outside linebacker big and powerful enough to set an edge on run plays at the line of scrimmage, often against lead blockers. In the Over front this responsibility had fallen to the left defensive end leaving the SAM spot more interchangeable with the weakside WILL, which is probably why the slighter Wright was able to play there more successfully in that scheme.

Personnel dynamics are never as simple as the term "first string", of course. As Rob Staton pointed out in Thursday’s Seaside Chats podcast, Irvin was often substituted at SAM in 2013 and 2014 by more traditional linebacker Malcolm Smith. But Irvin played 70 percent of defensive snaps under Kris Richard in 2015 because of the versatility he offered.

SB Nation’s Stephen White summarized it like this a couple years ago: Irvin as a defensive end prospect lacked bulk and a refined complement of pass-rush techniques, but "the reason why you would draft Irvin is because you expect that he wouldn’t come off the field on nickel." Richard loves to use disguised blitzes and coverages, and having a player with Irvin’s size and diverse skills helps free the coordinator to deploy a variety of wrinkled sets without tipping the opposing coaches what’s coming by always sending in specialized packages.

In that way, Irvin was like a Noh mask in Japanese theater, able to change the defense’s expression without requiring a "costume"-change. If SAM was a pivotal position as played by Bruce Irvin, the defense pivoted around his ability to combine multiple talents in one body.

However, as we know, Seattle’s new nickel plan involves using a linebacker in a hybrid-safety role, and that essentially suppresses the need for an every-down strongside ’backer. "[Brandon] Browner’s potential role as a safety in the Seahawks’ base defense likely correlates to Bruce Irvin’s departure," Sheil Kapadia speculated. "The Seahawks are obviously going to still play with four defensive linemen and two cornerbacks. Linebackers Bobby Wagner and K.J. Wright are not coming off the field. Neither are Earl Thomas or Kam Chancellor. So that leaves the SAM linebacker spot as the only one up in the air."

Seattle is not unique in trying to do this. The prototype of the trend is the Arizona Cardinals’ Deone Bucannon, the 2014 first round pick and former Washington State Cougar who, playing at a weight between 205 and 215 pounds, looks like he might belong to another species than the Pittsburgh Steelers’ 275-pound James Harrison, never mind the same position. Indeed the Cardinals list Bucannon as $LB for "money" or dollar linebacker (because, you know, a dollar is bigger than a nickel; Bucannon himself calls it "rover" or "landshark") and unless pro football goes back to being more run-oriented what we’re watching might be like the gridiron parallel of what occurred when the first lobe-finned fish crawled on land.

Extinction of the strongside linebacker is not complete, obviously, and the introduction of these dollar types has different utility in Arizona’s 3-4 (where Bucannon technically plays on the inside) than in the Seahawks’ scheme. But my suspicion is we’ll see a lot more of Browner, or alternates like Tyvis Powell—the undrafted free agent from Ohio State whose body measurables are almost identical to Bucannon’s—than we will see one of the players now practicing at SAM establish himself as a genuine regular in the lineup.

Powell took reps with the linebacker group as well as with defensive backs during OTAs, so picture him if he makes the team, or Pinkins or Tanner McEvoy, another undrafted "athlete" with 6-foot-6 size to match up with tight ends, or mayyyyybe even Stanley Jean-Baptiste, filling out this role in situations that call for base but Seattle wants to give a nickel look. Pinkins played in a system using a 3-3-5 nickel as the standard base at San Diego State; according to Scott Cohen of the P-I his position there was called "Warrior", simultaneously stacked in the box and guarding the slot. In Richard’s adapting defense there too may be little to distinguish SAM from the nickel safety.

It’s kind of asking for the opposite of what Irvin offered. Instead of having a trusty Swiss-Army knife for all purposes, training these guys for the base duties becomes like keeping a roll of duct tape handy only to bridge the packages when Seattle goes heavy, with say Cassius Marsh holding down the line of scrimmage across from Frank Clark’s penetrating LEO almost like 3-4 OLBs, and when it’s in the various nickel formations whether that means extra corners or safeties. As a teambuilding strategy, it almost dissolves the nominal position the way fullback has been a fraternity mostly disbanded by the advent of spread offenses.

And for the Seahawks’ purposes, with so many big contracts to balance already on defense, further minimizing SAM as a headlining job helps save capital like Russell Wilson’s freelancing and Tom Cable’s scheme allows Seattle to defray a lack of spending on offensive line. This development rather absolves the team of any charges of "disrespecting" Bruce Irvin when it declined to pick up his option or match his new deal. It’s not that Irvin wasn’t worth the money, more like his position fell out of pace with the value he commanded.

The cost then comes from holding so many roster spots for a position that appears to be vanishing. More than likely, even some of the chief candidates to inherit Irvin’s spot won’t make the Seahawks 53-man cut. Morgan’s experience and ability to backup both other linebacker jobs make him seems like a lock but he also doesn’t bring the situational upside some of his competitors do, while fresh all-around talents (McEvoy plays offense and defense) could take his place on special teams. But that’s a conversation for Kenneth Arthur’s bubble watch.

Tell us in the comments what you think of the evolution of the SAM and which guys you want to see crack the lineup.