Well, there is every reason to expect Rawls to be #1 on the depth chart, in which case it makes zero sense to sign Martin for the money that would require to play behind Rawls, and that was the point of my response to your post. I agree the Seahawks will likely add another RB for depth, but it would be very surprising if that was Martin.
Rawls looked pretty good for a fraction of a season (only 6 games with over 30 snaps, all the rest were 11 or less) where the defense probably wasn't keying on him like they would Lynch. I didn't do a lot of research (or any, tbh) into his catching or blocking, but I seriously think there's
at least a 50% chance he's not the starter next year. An UDFA with six real games under his belt who got injured... you don't go into a potential super bowl season with him as option #1 unless you are really, really up against the cap. RBs are relatively cheap. Someone with more experience + pedigree will be brought in and likely win that job. Maybe not Doug if he prices himself out, but very possibly a guy like Lamar Miller or Chris Ivory.
Rawls had more than 6 carries in 6 games. In those games, he had 776 YFS and 5 TDs. He had 100+ rushing yards in 4 of those games and 200+ in one of them.
He caught 9 of 11 targets for 76 yards on the season, so there is some potential for him in the passing game.
He led the league in YPC and ranked high in yards after contact, maybe #1, but I don't know where to find that data. Per Football Outsiders, he ranked #1 in DYAR and success rate and #2 in DVOA.
I think you are off base in your assessment that the only way he is the starter is if they are up against the cap. I'm not sure if you watched his games, but I watched all of them, and he looked as good as Lynch ever did. He got injured, but anyone would have been injured on that play, and the injury did not require surgery and should have no lasting effect.
Anyway, we can agree to disagree on this, but I don't see Seattle as a prospective landing place for any of Martin, Miller, or Ivory.