However, since his father Moronaga allied with the Retired Emperor Sutoku to trigger the Hogen no ran in 1156, Moronaga was held responsible for his association with his father, and his court rank was taken away from him before being exiled to Tosa no kuni (Tosa Province) (one theory stated that it was the Hata district within the same province).
しかし1156年、父の頼長が崇徳上皇と手を結んで保元の乱を起こしたため、その連座として師長は官職を剥奪されて土佐国（一説には同国幡多郡）に流罪に処された。