The Toros waived formed North Carolina guard Melvin Scott to make room for Williams who has not played in a NBA regular season game since severing a nerve in his leg, fracturing his pelvis and tearing three of the four main ligaments in his left knee in a motorcycle crash in June of 2003.
Williams will report to Austin on Friday and will begin practice with the team on Saturday morning.
Williams' No. 22 jersey is one of a handful of retired numbers. He was a two time National Player of the Year at Duke.