Withrow worked out for the Seahawks on Wednesday. Canter said Withrow will fly to Seattle and sign with the team once he passes a physical.
Concerns about the shoulder of guard Mike Wahle caused the need for an extra offensive lineman. If Wahle is unable to participate in the early part of training camp, second-round choice Max Unger may have a chance to get the starting job at left guard.
John Clayton is a senior NFL writer for ESPN.com.