In a one-gap scheme all front seven guys need to keep their place -- the soccer folks have a phrase called "keeping your shape" that applies here -- so they don't unintentionally create cutback lanes.
I have been harping on this for a while as a major problem I have been seeing with the defense. Guys doing to much free lance trying to make the tackles that they end up losing their responsibilities and allow the back to cut back on them. I want guys to be aggressive but you have to play this game smart as well and know what your responsibilities are and play within the frame work of the defense