(AP) — A new defensive coordinator, an infusion of youth and the return of Dre Greenlaw had San Francisco 49ers star linebacker Fred Warner raving about how much fun he was having anchoring one of the league's more surprising units this season before heading out on the bye.Warner's enthusiasm, and the potential of the Niners defense, only got higher after the team made a big move during the week off to bring back three-time Pro Bowler DeForest Buckner to help anchor the defensive interior.