The San Francisco 49ers spent the last couple years trying to implement a base 4-3 Under defense, but to no avail. So instead of trying to fit a bunch of square pegs into round holes, they brought in a couple new position coaches to help make adjustments and change the overall philosophy.
Much has been made of Kris Kocurek with his Wide-9 and the interchangeable safeties that Joe Woods is pushing for, but not much has been said about the defense as a whole. In previous years the nose would line up in the A-gap (between the center and guard), the big end would line up in the C-gap (between the tackle and tight end), and the Sam lined up on the outside of the TE, but with the change in the defensive line’s alignment the nose will move over and line up directly over the guard while the big end will kick out to the outside of the TE which forces the Sam LB back off the line and into a more traditional 4-3 OLB role, mirroring the responsibilities of the Will.