So why does Arik Armstead fit in so well with the 49ers? Because they play a 3-4 defense built upon the George Seifert-Bill Parcells style of defense. In that scheme, the defensive linemen are sacrificial lambs; grabbing offensive lineman and occupying them while the four linebackers run and make tackles.
Now with new defensive coordinator Eric Mangini, who is only a branch or two removed from the root of the Parcells’ coaching tree, the 49ers defense is even more entrenched in 3-4 principles. That’s where Armstead comes in. He came from a similar system at Oregon, which is key.