I can see some similarities in the Seahawks' 2014 unrestricted free agent class with their 2015 class. Consider this:
2014 UNRESTRICTED FREE AGENT CLASS (15 players)
CB Brandon Browner, CB Walter Thurmond, S Chris Maragos, Edge O'Brien Schofield, DT Clinton McDonald, DT Tony McDaniel, DL Michael Bennett
QB Tarvaris Jackson, TE Anthony McCoy, TE Kelen Davis, WR Golden Tate, FB Michael Robinson, OT Breno Giacomini, OL Paul McQuistan, K Steven Hauschka
From the list of 15 players that were set to hit Unrestricted Free Agency, the numbers seem pretty balanced on offense and defense (seven each). The Seahawks re-signed six players -- Michael Bennett, Tony McDaniel, O'Brien Schofield, Tarvaris Jackson, Anthony McCoy, and Steven Hauschka.
In 2014, the Seahawks also inked three significant contract extensions: Richard Sherman, Earl Thomas and Doug Baldwin. These "Big Three" were done before Richard, Earl and Doug were eligible for unrestricted free agency (originally in 2015). Partially, to make room for the three extensions, the Seahawks cut three key contracts early.
2014 CAP CASUALTIES
WR Sidney Rice (2 years early), DL Red Bryant (3 years early), DE Chris Clemons (1 year early)
Fast Forward to 2015, and the key unrestricted free agents look something like this:
2015 UNRESTRICTED FREE AGENT CLASS (14 players)
QB Tarvaris Jackson, OG James Carpenter, OL Lemuel Jeanpierre, OT Eric Winston
Notice only four on offense. If the Seahawks keep Terrelle Pryor, than that would be five. If you want to count Anthony McCoy for this discussion, then it could be six players on offense.
CB Byron Maxwell, CB A.J. Jefferson (if he makes the team), S Jeron Johnson, LB K.J. Wright, LB Malcolm Smith, Edge Cliff Avril, Edge O'Brien Schofield, DT Kevin Williams, LS Jermaine Gresham
Again, this list will change with cuts and injuries -- but it is looking somewhat similar in numbers to 2014, although the offensive roster is controlled a bit better. Notice that not one running back, tight end, or wide receiver is set to be an unrestricted free agent in 2015.
The three players that I can see get extensions early are Russell Wilson, J.R. Sweezy and Bobby Wagner. All three were in the Draft class of 2012 and set to be UFA in 2016. I can see these three get extensions a year early like Sherman, Thomas and Baldwin did.
Of the list of 2015 unrestricted free agents, I believe Seattle will look to strike new deals with Cliff Avril, K.J. Wright and James Carpenter (and Clint Gresham), and I can see the young UFA finding better pastures elsewhere (guys that have never hit their first big contract like Byron Maxwell, Jeron Johnson, Malcolm Smith, O'Brien Schofield and Lem Jeanpierre). Guys like Tarvaris Jackson, Eric Winston and Kevin Williams will probably spend the rest of their NFL career on shorter, modest deals as they are older players now.
To create cap room, I believe there will be at least two cap casualties in 2015 -- and the list of possibles for those two is a list of four players. I do not anticipate all four being cut a year early. I believe one will come from offense and one will come from defense. There could possibly be three depending on how the contracts go with the younger players signing extensions and new deals.
TE Zach Miller (UFA in 2016), RB Marshawn Lynch (UFA in 2016)
DT Brandon Mebane (UFA 2016), DT Tony McDaniel (UFA 2016)
Zach and Marshawn are both 28 years old now. Brandon and Tony are both 29 years old now. I believe the health and performance of each specific player on the 53-man roster in 2014 will make all the decisions above more plain.