Sullivan underwent a lumbar microdiscectomy on Sept. 9 for a herniated disc.
Sullivan first encountered the problem as the Vikings were preparing for the Hall of Fame Game in which he and starters played the first series. Sullivan and the Vikings training staff tried giving the injury time, treatment and therapeutic methods that included two epidurals, but placed him on the injured reserve-designated to return list. That designation will allow him to return to practice after six weeks and game action after eight weeks after first placement if he is cleared (click here for a rules refresher).