Defensive coordinator Jim Mora Jr. returns for his fifth season in that capacity with the 49ers, where he'll be joined by associate head coach/linebackers Greg McMackin.
"We are going to be a very aggressive defensive football team," Erickson said. "That is how my defenses have been every place I have been. We've got speed. We are going to be aggressive. We are going to blitz. You'll see us blitz and play zone behind it. You'll see an aggressive football team. That is Jim Mora's, mine and Greg McMackin's philosophy. You will see a lot more pressure. We can run. You got to look at your team and find out what they do best. The thing that we do best is run fast. We have good speed, especially at linebacker."
Erickson said the staff will determine during the course of training camp how much - if any -- to employ a 3-4 defense. The 49ers have been a 4-3 team since the middle of the 1993 season.