The defensive line is tough to project. We know the starters, but will the starters rotate with similar role players or will their be more specialization? I do not know. Let's explore what that means.
Starter: Chris Clemons
This is the easy one. Not too many players on the Seahawks roster fit the profile of a stand up end. Seattle will retain two or three. I will give Foley the benefit of the doubt and project Clemons, Reed and Foley to stick and Davis to be signed to the practice squad.
Starter: Brandon Mebane
Backup: Craig Terrill
And now it gets interesting. Mebane is the only defensive lineman on the roster that fits the converging needs of Pete Carroll and Dan Quinn. Or, to put it another way, if Mebane missed a game, would you trust a weak side comprised of Clemons and Terrill? Pitcock and Lewis are penetrating, single-gap tackles. Any one of Terrill, Pitcock and Lewis could be valuable as a rotational player, but who backs up Mebane? If Vickerson started in Brandon's place, then the pass rush is hamstrung. Quinn's need to make the line massive and Carroll's need to make the line disruptive are at odds.
Hopefully Brandon can prove superhuman, stay healthy and render this discussion irrelevant.
Starter: Colin Cole
Backup: Kevin Vickerson
Seattle lacks a competent backup for Mebane. It appears to have no one capable of backing up Cole and Vickerson. If both were injured, it could move Bryant inside and play E.J. Wilson at end. That might be the most elegant solution, but it wouldn't do the run defense any favors. It also might move Mebane to over tackle and start Terrill at under tackle. That might work, but it creates the nightmare Terrill-Clemons scenario. Hopefully one of Cole or Vickerson is always healthy.
Left Defensive End
Starter: Red Bryant
Backup: E.J. Wilson
This is pretty straightforward, apart from what do with Jackson. According to listed weight, Bryant is 321, Wilson is 289, Rose is 291 and Jackson is 270. That makes Jackson the misfit. Jackson is also the best talent. He is not the best player. He may be the worst. But he is the best talent. So what do you do with him?
That strikes to the core of the debate. Seattle's base defense is a Leo end and three defensive tackle types. When it flexes into nickel and dime, it could rotate in players like Pitcock and Jackson, but the cost of creating multiple looks is less depth behind the starters.
When Carroll ran this system at USC, depth was never a concern. The Trojans retained 100+ players on roster. Defensive formations could range from a 5-2 to a 3-3 stack in the same game, and Carroll could field specialized personnel for each look. Which isn't to say he did this. Only that he did not need to consider personnel when defining scheme. He could impose a scheme and find the talent to make it work.
That is not possible within the constraints of a 53 man roster. A team's base defense also dictates its nickel and dime packages. That is why a 4-3 typically flexes to a 4-2 or a 3-3 on nickel downs, while a 3-4 flexes to a 3-3 or a 2-4. If you start four linebackers, you need more linebacker depth. If Seattle is going to start three massive defensive tackles, it needs to back those players up with massive defensive tackles. But it hasn't. It has Terrill, Pitcock, Lewis and Jackson.
There is no way for an NFL team to be fully prepared for every injury. The limits of a 53 man roster prevent that. The more generalized a position, the easier it is to fill. The more specialized a position and the more masters it must serve, like the curious pairing of Carroll's 4-3 under and Quinn's penchant for 3-4 personnel, the harder it is to fill. That might create a capable starting defense, but it taxes the depth. Depth might be a concern all season and a focus of the off-season. Thus are the growing pains of a coaching change.