Board Thread:Questions and Answers/@comment-6019258-20130325050319/@comment-7658432-20130401011605

Yes, maybe he acquired a gigai that's same to Isshin's and Urahara's so he gradually lost his Shinigami powers and learned to focus on his Fullbring powers. Remember he took Ichigo's Fullbring and combined it on his own? That's when the bankai thing started as Ichigo's Fullbring contains traces of his Shinigami power.