Velasco injured his Achilles in Thursday's 22-20 loss to the Baltimore Ravens. Velasco is the second Steelers center to be lost for the season. Maurkice Pouncey tore the ACL in his right knee eight plays into the opener against the Tennessee Titans in September.
The Steelers signed center Eric Olsen and offensive tackle Rashad Butler to add depth to a depleted line. Olsen played in 16 games, with four starts, for the New Orleans Saints in 2012. He was released by the Saints in September.
Butler has played in 50 games over the last seven seasons, most recently for the Cleveland Browns.
Copyright 2013 by The Associated Press