David Arkin never played a down for the Cowboys in 2 1/2 seasons. They released the offensive guard on Saturday, clearing the way for safety Jakar Hamilton to be moved up from the practice squad. Starting safety J.J. Wilcox sprained his knee in practice Thursday and will miss at least this week's game against the Lions, necessitating the move with Hamilton. Rookie Jeff Heath will make his first career start Sunday in his homecoming game. Hamilton is an undrafted free agent from South Carolina State.