UPDATE 1:44 PM:
Per Ian Rapoport of NFL.com, the recently cut Bills running back Fred Jackson is flying in this morning to meet with the Seahawks and is expected to sign with the team.
Fred Jackson is a 34-year old running back with a very unusual path, playing for the Sioux City Bandits in the NIFL and Rhein Fire in NFL Europa before catching on in the NFL. He's been an all-purpose back for the Bills, with a couple of outstanding seasons in 2009-2011, serving as a solid pass-catcher, runner, a great blocker and even a special teams player.
He ran for 43 yards and a touchdown against the Steelers in preseason before being a surprise roster cut. The fact that a 34-year old RB being cut can be a "surprise" speaks volumes to what they think about Fred in Buffalo, but they also saved $2.5 million in cap space by cutting him. He was very popular in the locker room, as evinced by the reaction of safety Aaron Williams, as well as other teammates. Marshawn and Fred played together in Buffalo.
Why the Hawks are looking to sign a 34-year old running back is another question. Fred would presumably come cheap so the money is not a major concern, but the interest expresses a low confidence in the running backer depth beyond Marshawn Lynch. From all reports, the Seahawks are satisfied in the reliable Robert Turbin, but Christine Michael is still a work in progress after two years and Thomas Rawls has not shown much to prove he's an NFL-caliber back. But the question of who would fall from the 53 for Fred Jackson is not a simple one: it's easy to say Christine Michael's window is closed and he's gone, but in reality Fred would fulfill the same role Turbin currently does and is probably better at it than Turbin.
Fred Jackson can run, catch, block, play special teams and do it all reliably, a strong option especially on third downs as a very strong pass blocker and catcher. He would also provide another veteran leader in the locker room, one that lead back Marshawn Lynch respects. Signing a 34 year old running back whose numbers do show a downturn (3.7 YPC last season, and yet 66 catches for 501 yards) is certainly not an expected move, but with Marshawn's back problems always a concern it looks like the Seahawks want to explore more dependable options behind him.
Jackson averaged 8.9 yards after the catch per reception last year, forcing 19 missed tackles along the way. Only Le'Veon Bell, Eddie Lacy, and Matt Forte forced more missed tackles on catches in 2014.