The importance of the defensive line to the Seahawks' prospects in 2009 cannot be under estimated.
The Jim Mora led defense will rely on the defensive line to generate a pass rush and take up blocks, freeing the linebackers to make instinctive plays and taking pressure away from the previously over worked secondary.
Let's look at how the line will function including rotation policies, individual roles and the key personnel involved.
In recent years Seattle has used a rotation policy with it's defensive tackles.
This is likely to increase in the future, so don't expect the DT's to feature in more than 30 snaps per game.
Last year Brandon Mebane registered 5.5 sacks in a role predominantly designed to carry blocks and draw attention.
Having signed Colin Cole (6'1", 330lbs) in free agency and with Red Bryant (6'4", 318lbs) returning from injury, this allows the team to be more flexible with Mebane.
He'll likely play a bit more three technique in 2009 to take advantage of his speed from the snap and ability to shoot gaps and penetrate.
Cole and Bryant will be used predominantly as a one technique.
A key free agent signing this off season, Cole signed an eye catching $21.4m deal to move from Green Bay.
He has the bulk to occupy blockers in the interior freeing up attacks from the edge.
If Cole can draw enough attention in the middle, taking on a guard and center combination and perhaps moving off to a tackle—this forces the tight end to cover the defensive end and potentially creates opportunities for the teams linebackers to attack the backfield.
Craig Terrill will also be worked into the teams' rotation. He recorded two sacks and returned a fumble for a touchdown in 2008.
Newly acquired Cory Redding is set to feature more as a defensive end.
However, there's a good chance he'll slip inside on third down in passing situations.
The rotation policy has led to some difficulties in the past.
The strictness in which it was enforced last year in particular often saw Terrill (6'2", 295lbs) on the field in red zone defense against the run, not ideal considering his lack of size.
Whether or not we see a more clinical approach to the rotation policy—or may even more time on the field for the key figure's (Mebane and Cole) remains to be seen.
Having acquired a solid stable of ends we are likely to see a comparable rotation policy at the DE position too.
Patrick Kerney has missed 16 games in the last three years and is currently rehabbing ahead of training camp.
The Seahawks will be wary of over working Kerney, clearly the teams best pass rushing end, whilst also maximising his talent to generate a pass rush.
When Kerney was placed on injured reserve after week seven in 2008, the team struggled to generate any kind of pressure on the opposition quarterback.
The trade to bring in Cory Redding should help.
Although used mainly as a defensive tackle during his career, at 6'4" and 295lbs he's got the frame and speed off the edge to adjust to his new task.
It'll be interesting to see if Redding spells Kerney to consistently get that presence every snap, or if they'll play across from each other in a tandem.
Second year DE Lawrence Jackson will be hoping for greater success in 2009.
Thrust into a starting role as a rookie, Jackson struggled to provide a legitimate pass rush but was quietly effective against the run.
Likely to be used regularly in run defense, he's shown the ability to carry blockers which could provide plenty of opportunities for Aaron Curry to get to the ball carrier.
Darryl Tapp will also be hoping to create an impression heading into a contract year.
Benched in favor of Jackson originally, Tapp eventually featured with greater regularity in 2008 due to Kerney's absence.
Like Jackson, Tapp is capable in run defense and will draw some attention from blockers.
He's also shown the ability to get to the passer, registering seven sacks in 2007 and 15.5 in his three year career.
The Seahawks may also choose to retain Baraka Atkins, a 2007 fourth-round pick who picked up two sacks last year.
Expect to see different lineups at end, with Kerney spelled by Redding at left end but also featuring across from the former Lion at times.
Jackson and Tapp will likely rotate at right end depending on the situation.
On third down passing scenarios, Redding will move inside with Kerney and Tapp the likely ends. Aaron Curry will also move closer to the line of scrimmage and rush from the edge.
The importance of the defensive line
Under the stewardship of defensive coordinator John Marshall last year, the Seahawks failed to generate a sufficient pass rush in the absence of Patrick Kerney.
It also didn't help that the team's offense ranked dead last in time of possession—the Seattle defense was on the field more than any other in 2008.
To compensate for the lack of pressure, Marshall instructed the team to blitz often.
This left the secondary exposed and over worked, whilst making the team predictable and fully committed at the front.
Head coach Jim Mora will take control next year with help from new defensive coordinator Gus Bradley.
The main aim will be placing a greater reliance on the defensive line to create a pass rush, freeing the linebackers to make instinctive plays.
There will be less blitz, with a greater responsibility in coverage from the linebackers in the featured cover-two.
Of course, all of this can only work if sufficient pressure is created from the front.
If the Seahawks fail to get the required pass rush from the defensive line, this will restrict the level of freedom afforded to the like of Aaron Curry and Lofa Tatupu.
A lot has been spoken of the switch to the cover-two and much investment has been placed in the linebackers.
However, the key to functionality on defense remains with the defensive line.