Hightower, 29, was the Arizona Cardinals' fifth-round draft pick in 2008 but hasn't played in an NFL game since tearing his ACL on Oct. 23, 2011. He signed with the Saints during the offseason and mounted a comeback attempt in camp.
After making the 53-man roster, Hightower was released one day before the Saints opened the season on Sept. 13 at Arizona. Hightower was already in Phoenix by the time the move was announced and watched the game with Saints coaches in the press box.
Robinson was averaging seven carries a game and two catches a game over eight games this season.