Per Danny O'Neil: Here

Seahawks release FB Justin Griffith, sign Kyle Williams to the active roster.

Weird, since just yesterday came this blurb about practice:

"FB Justin Griffith (knee) did a little in individual drills, but nothing in team drills. "He's made some strides," coach Jim Mora said"

and I thought Griffith was a big part of Knapp's running game plan since he knew Knapp's system so well. That says to me either they really like Schmitt stepping in, that Griffith's knee was more injured than they were letting on or that the team really needed Kyle Williams.