Whenever a follower's performance slips, for whatever reason, and ability or motivation falls, the leader reassesses readiness and moves backward along the curve, providing the direction and support the present level needs. The authors' cases: a normally self-directed person hit by a family crisis may need a moderate increase in both structure and support until composure returns; a grown child in difficulty may need renewed support; a group that is failing after warm, permissive leadership needs structure first and support again only when it begins to take responsibility. The CLS summary adds the teacher promoted to principal, who needs the leader to move from S4 back to S3 or S2 on the new responsibilities. In regression the issue is usually unwillingness rather than insecurity.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.