McCallum will take over the spot Cory Joseph's departure left open in the rotation.
The Spur will trade a future second round pick for Kings backup point guard Ray McCallum, reports ESPN's Marc Stein.
San Antonio lost Cory Joseph to the Raptors in free agency and needed a third point guard behind Tony Parker and Patty Mills in case of injuries. No names emerged in free agency rumors but the need for depth at the position was evident. The Spurs could have settled for a veteran on his last legs but have instead traded for the 36th pick of the 2013 draft.