In a 3-4, the DT is the cornerstone of the defense. Do you really think it is wise to commit this team to a defense, and 5 million in salary, to a guy who has never played to position and has shown little, if any, heart?
Besides, Williams is tall and slow off the ball, even when he knows the snap count. I think opposing guards/centers will find it relatively easy to get under him, get leverage and move him just enough to create holes. Thats not to mention that our DEs and LBs are small for the 3-4.