The team announced the move Friday. Loper spent last season with Detroit, where he started five games for the Lions. He played the previous four years with Tennessee. He appeared in 40 games for the Titans, but did not make a start.
Brandon Rodd had been the only true guard backing up Robert Gallery and Cooper Carlisle before the move. The Raiders have several other linemen capable of playing guard, including rookie tackle Bruce Campbell, veteran tackle Khalif Barnes and center Chris Morris.