Nathan Walker extension: What does this mean for the 4th line?

St. Louis Blues F Nathan Walker | Leila Devlin/GettyImagesDoug Armstrong and the St. Louis Blues just agreed to a contract extension with depth forward Nathan Walker.

This move signals corresponding changes for the 4th line and the roster as a whole. What are the most important aftereffects of the Nathan Walker extension?

Identity hockey: An extension well-earned

Doug Armstrong spoke about the importance of a player like Walker in the infamous "W-T-F" line last season. Walker always announced his presence early and often on the ice, serving as the team's enforcer despite his 5'9" size.

Walker's style of play meshes exactly with what Doug Armstrong and Jim Montgomery are trying to build in St.…