User blog comment:Godisme/My Take on Isshin/@comment-1393830-20100328190139

I doubt any of that. Isshin has never been seen with the Vizard. If the Vizard knew him, Shinji would have known the tremendous power he felt the day grand fisher was killed was Isshin's. Also I doubt he was 11th squad captain as Zaraki brutally killed the former captain and If I am not mistaken, we get a small glimpse of him at one point though this may just be the anime. If he was a captain it was most likely 10th because of Toshiro's age