Embodiments described herein include a method comprising: providing a treatment fluid comprising an aqueous base fluid, a viscosifier-scale inhibitor agent, and a breaker, wherein the viscosifier-scale inhibitor agent comprises a polysaccharide gelling agent grafted with a chelating moiety; introducing the treatment fluid into a subterranean formation, wherein the polysaccharide gelling agent increases the viscosity of the treatment fluid and the chelating moiety remains inert; breaking treatment fluid with the breaker so as to reduce the viscosity of the treatment fluid and chemically release the chelating moiety from the polysaccharide gelling agent; and inhibiting scale within the subterranean formation using the chelating moiety.