Looking to improve its beleaguered defense, Nebraska officially named Bo Pelini as Bill Callahan's successor on Sunday. Known as a defensive guru, the 39-year-old Pelini returns to Nebraska after spending the last three seasons as the defensive coordinator at Louisiana State. The announcement came one day after Pelini's Tigers defeated Tennessee, 21-14, in the Southeastern Conference championship. "We need a head coach with strong defensive credentials and great leadership," Nebraska interim Athletic Director Tom Osborne said.