Offensive linemen move around the line frequently, maybe especially at Notre Dame. From tackle to guard (Tommy Kraemer last year, for example). From guard to tackle (Alex Bars could have made that move last season if an injury created the need). From guard to center (Nick Martin’s NFL career). Those moves are usually either a flip from one side of the line to the other, or only one spot in or out. A move from right guard to left tackle would be unusual, as would be a move from left tackle to center.
It is that exact latter move that the Irish have executed to find their surprise starter at center, sophomore-to-be Jarrett Patterson.