Depth is important in the NFL. While having a handful of 'elite' players and a very good quarterback may be at the top of the list of things needed to achieve sustained success in this league, quality depth is up there as well. It's a long season. Injuries happen. You simply need players that can come in in relief of your 'stars' or 'starters' without seeing a huge drop-off in effectiveness (some drop-off is a given, particularly if you're replacing a 'star', but it must be manageable).

Seattle's depth last year was integral to their championship run -- major injuries affected the offensive line, including both tackle spots, a major injury kept the Seahawks' most explosive receiver off the field for all but two/three games, and the cornerback depth was again tested with two more suspensions. The Hawks' depth players stepped in and proved to be up to the task, and in at least one case, proved to be better than their predecessor (Byron Maxwell comes to mind).

You may have seen my series on positional group depth from over at the SBNation Mothership - in it, I tried to put teams into categories based on their depth and talent at each spot. In those rankings, I placed Seattle's defensive line and running backs groups into "Wild Card" categories, meaning they have the chance to be elite but have some question marks going into next season. I put their linebackers into the "Damn Good" category, their tight ends and their wide receivers into the "Contenders" category, and noted that they're in good shape with a veteran/homegrown backup quarterback in Tarvaris Jackson. Obviously, I put their defensive secondary in the "Elite" category.

The only Seahawks' positional group that didn't make my "best depth" lists was the offensive line. That group has the potential to change this year, with some pieces falling into place and with some much-needed continuity resulting from better luck in the health department, but overall, Seattle has to feel good about where their roster stands.

Which brings me to my point: there is more than one way to look at roster depth. Instead of breaking down each position group, I thought that Pat Kirwan has a pretty interesting method:

In my opinion there are 13 categories that have to get a positive answer for a team to qualify as having solid roster depth.

Nice. The first?

The backup quarterback. A capable backup QB that can go at least 2-2 in a four-game stretch qualifies as a good backup.

As I wrote last week regarding Seattle's backup situation,Tarvaris Jackson has played seven of his eight seasons in the NFL under offensive coordinator Darrell Bevell, first in Minnesota, then later in Seattle. His depth of knowledge into Bevell's playbook -- the language and concepts therein -- is pretty unmatched. Like Matt Flynn in Green Bay, Jackson seems tailor-made to be a backup in Seattle's system; he possesses a strong arm to take deep shots downfield (a Seahawk staple), has mobility to run the bootleg game they adore and has become very disciplined later in his career, which fits Pete Carroll's "protect the football" mantra perfectly. He's highly respected by his teammates, something that certainly matters if he's ever asked to command the huddle on meaningful snaps, and has taken a lot of reps with Seattle's offensive weapons over the past few years.

Jackson has 34 career starts, but he only played in garbage time in 2013. That said, he made the most of it, posting a 140.2 passer rating on 10-of-13 passing for 151 yards and a touchdown. During Seattle's 2013 preseason, Jackson completed 26-of-36 passes for 9.9 YPA, three touchdowns and no picks (131 rating). Those stats don't matter, obviously, but they do show his comfort level in the Seattle system.

So, what about the other 12? Let's go through them. It's worth pointing out that Kirwin listed Seattle in the top spot, tied with Cincinnati.

1. Does your team have a real swing offensive tackle, a guy that can play left or right tackle and has experience?

Debatable, but things are favorable on this front. A lot depends on whether Michael Bowie or Justin Britt ends up at right tackle, but with the combination of the three -- Britt, Bowie, and Alvin Bailey, Seattle has two 'swing' tackle types that could come in and play (and have) when injuries happen to starters. I wouldn't list Seattle's swing tackle situation among the league's best, but they are set up to absorb injuries to Russell Okung if they have to cross that bridge.

2. Does your team have a solid inside offensive lineman that can play guard or center?

I would point to Lemuel Jeanpierre here. Jeanpierre has started eight games for the Hawks in his three seasons, and while he's not as technically sound or efficient as a healthy Max Unger (obviously), he has acquitted himself well when asked to come in in relief. Lem plays both guard and center. Greg Van Roten is another option here as a guy with NFL experience at both guard and center, and Jared Smith is the darkhorse as a developmental type.

3. Is there a quality second running back that can deliver a 100-yard rushing day if he had to start?

I actually think that in a sustaining role, Robert Turbin could be this guy, and right now, he probably would be. Turbin is a battering ram with some nice speed, and if Marshawn Lynch went down, I think the Hawks would not hesitate to hand it off to him 30 times in a game.

Christine Michael, of course, is an exciting prospect as well, and assuming he has the mental part of the game down, is definitely a guy that could rush for a c-note if given the opportunity. You could argue that Spencer Ware is a dark horse in this group too.

4. Is there a good second tight end on the roster?

There's a second and third good tight end on this roster, in my opinion. Luke Willson is the likely go-to guy if Zach Miller were to get hurt, but the return of Anthony McCoy adds some excellent depth as a third string player with unlimited physical ability (potential, anyway) and years of experience in the system.

5. Can the third wide receiver step up and start in the two-WR packages if a starter went down?

Assuming Percy Harvin and Doug Baldwin are your one-two punch, yes, Jermaine Kearse could come in and be that guy. In fact, Seattle uses such a wide variety of personnel packages and rotates their players on to the field so much, that this would not even be out of the norm. Getting Sidney Rice back to full health just adds depth and experience to the group, and the two rookies in Paul Richardson and Kevin Norwood round out the depth. Ricardo Lockette is experienced as well, and could factor in.

6. Does your team have a designated pass-rush specialist who could play the early downs if need be?

Cliff Avril.

If he gets hurt, Bruce Irvin could be this guy, and Malcolm Smith could play SAM. Seattle has options in their pass rush packages.

7. Is there a third defensive tackle that not only plays in a rotation but could play the whole game if need be?

This is a question mark of sorts because of Seattle's heavy rotation, but the depth on the line is solid. Both Kevin Williams and Tony McDaniel have proven themselves in this category as guys that could be called upon to play a bigger role (more snaps) if injuries happen. Guys like Greg Scruggs, Jesse Williams, Jordan Hill, and Jimmy Staten could also step in for major snaps if need be, but their effectiveness in that role is a big question mark.

8. Is there a quality nickel corner on the roster, since most teams are at least 50 percent sub defenses?

Jeremy Lane figures to be the inside guy this year, and Seattle is also taking a long look at Philip Adams, A.J. Jefferson, and Akeem Auguste for this role. They should be just fine, even after losing Walter Thurmond to free agency.

9. Is there a fourth corner for dime packages?

Assuming the rave reviews that Tharold Simon is receiving early in camp don't end up being way off base, Seattle may be in good shape depth-wise at the cornerback spot. Philip Adams, A.J. Jefferson, and Akeem Auguste also factor in to this competition, and DeShawn Shead has experience playing cornerback. The Hawks want to groom rookie Eric Pinkins to play both corner and safety. Terrance Parks has played both corner and safety.

10. Is there a third safety for big nickel defenses?

Jeron Johnson figures to be this guy, and has experience over the past three seasons. DeShawn Shead is another guy that could factor here, as could rookie UDFA Dion Bailey, if he makes the roster. Terrance Parks has been getting nice reviews in camp, and rookie Eric Pinkins may surprise there -- it's the role he played in college, more or less.

11. Is there a return specialist that can either handle both punt and kick returns or contribute as a real position player?

Percival.

12. Does your team have a special teams linebacker that leads the specials and can play inside linebacker in a pinch?

This has been Heath Farwell, and the steely vet has done a good job of it for the past few seasons. It's up in the air if Farwell will make the roster this season with guys like Korey Toomer, Brock Coyle, and Horace Miller providing some competition. I think that Kevin Pierre-Louis factors in here, because if Bobby Wagner were to get hurt, the Hawks would slide K.J. Wright to the MIKE spot and rotate Toomer or KPL into the OLB spot. Regardless of how it shakes out, I'm pretty optimistic about the linebackers group, and in particular, think their speed/athleticism on special teams is going to be absurd.

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So, with varying strength, I would answer yes to every question. I think #1 and #10 are the biggest question marks at this exact moment, but that stuff will get ironed out in training camp and preseason, most likely.

If any of you guys/girls want to make your list of 12, do so in the comments below.