Salary cap relief. That means one or more of the following:
DE (Clemons 9.6m/Bryant 8m)
DT (Mebane 5.5m)
WR (Rice 9m/Tate 5m?)
TE (Miller 7m)
OL (McQuistan 3m/Giacomini 4m)
Bold = little to no dead money cost
None of the needs listed above are worth more than not being able to resign Sherman or Thomas. Some of these can be renegotiated or cut and resigned later for less. But likely not all of them. Some of these salaries absolutely much go next year.
Figure 3 of these if you believe Bennett needs to be resigned. He'll command 6m+, up from 4.8m this year.
I'd say WR is highly likely to be reworked. For 2 specific reasons. One, the quality at the position is very very strong, and should have several outside WR options available to replace Rice. Two, the WR production is modest. Partially by design. Rice's contract is enormous and is not even enough to just extend Sherman on it's own.
Some of these moves will happen before the draft. For example, Bryant has a 3m roster bonus for the 2014 season. Meaning he'll earn it the 2nd day of the league year which will be early March. For Seattle to rid itself of this unrecoverable expense, they'll have to cut him by that time. If Seattle harbors hopes of resigning Tate, they'll have to make this room early -- maybe even day 1. At any rate, we will know well ahead of draft time if that vacancy remains since he'll be gone early and we'll have had to sign a replacement well ahead of the draft if that was going to be the case.
Additionally, McQuistan and Giacomini are UFAs in 2014. So technically, they are already not on the roster next year. If they aren't resigned, there are 2 open positions on the OL that will need filling regardless if Bowie/Bailey are elevated.
UFAs that will merit consideration to resign:
Thurmond
Tate
Browner
Bennett
Also consider, that Baldwin will be an RFA. I don't see any way we have Clemons or Bryant on this payroll, as those two alone would allow us to resign all 4 of those UFAs and extend Thomas too. Rice and someone else will be required for Sherman. I expect Avril is the Clemons replacement for 2014 and his cap value is already factored in as he's on the club and his guaranteed value prohibits cutting him.
I'd say WR and OL is likely as there could be more than one vacancy for each of those units. Some of those vacancies may be filled by 1 year show me contracts -- not unlike Bennett this year.