Derek Walker was considered a finished product by scouts. That's a double edged sword in scout speak. Yes, knowing how to play football is nice, but everyone wants the next Antonio Gates. The player that doesn't know how to play football, but turns out to be natural. A finished product isn't expected to develop. They will take their relatively small talent and take their generous skills and play for a preseason before getting cut. Mike Hass is a finished product.
Ironically, Walker joins Hass on the Seahawks practice squad. There they can hone their finished skills and hope maybe they're not so finished. Hass is probably playing out his time before he signs somewhere as a wide receivers coach. Walker can still hope for better.
He's a big kid and his future lies in playing strongside defensive end or bulking up and playing tackle. On another roster, he could rotate as a 3-4 end. Walker is a little tall for tackle, and whether that is truly meaningful or not, it's meaningful for how coaches view him. He would have to play an under or three-tech tackle. Walker doesn't need to be told that making the 53 man roster is no guarantee he ever makes an NFL team. He just needs to keep carrying helmets and kicking ass, and keep hoping scouts missed something big looking for the next big thing.