The San Francisco 49ers have claimed rookie outside linebacker Thaddeus Gibson off waivers from the Steelers on Monday. Gibson, a fourth-round pick out of Ohio State, was placed on waivers Saturday when the team signed defensive lineman Steve McLendon to the active roster from the practice squad. Gibson had been inactive for the Steelers first 6 games of the season and was deemed the low man on the totem pole of a deep linebacking unit by head coach Mike Tomlin. The move was needed to add defensive line depth with both Steelers defensive ends Aaron Smith and Brett Keisel sidelined with injuries. Besides the 49ers, the Philadelphia Eagles also had put in a waiver claim for Gibson.