Jefferson (back) has yet to fully participate in team activities and remains without a timetable for his return, Erik Slater of ClutchPoints.com reports.
Coach Jordi Fernandez confirmed Friday that the rookie is still dealing with back stiffness and isn't ready to return, although Jefferson has participated in portions of team activities and has been doing conditioning work. Fernandez was also unable to confirm whether Jefferson has undergone imaging. With Brooklyn's regular-season opener against Charlotte scheduled for Wednesday, it's safe to rule him out.