Warner knows 49ers must improve defensive effort before Super Bowl

SANTA CLARA — In the second quarter of the 49ers' NFC Championship Game win over the Detroit Lions at Levi's Stadium, Detroit running back Jahmyr Gibbs scampered 15 yards, barely touched, for a touchdown. During the play, the 49ers' defense showed an alarming lack of effort, which allowed the Lions to take a 14-point lead. On Thursday, 49ers coach Kyle Shanahan was asked if he was concerned about the play and the overall effort of his defense. "I know it looked bad on the clip that you guys have and stuff," Shanahan said. "No, it's not our culture. We don't want to have one play like that. I think we had about two to three in that game, which is too much for us. We don't want to ever have one." Several 49ers defenders lunged for the Lions ball carrier but did not bring him down. Crediting the players for missed tackles might be too generous as there did not appear to be attempts to make a full tackle. "But it wasn't just the D-Line," Shanahan said. "There were a few backside people who weren't going and they were expecting someone else to make the tackle. Whenever you're expecting someone else to make the tackle bad things happen. " Rather than singling out individual players,...