User blog comment:Sicarius001/Royal Guard and Eighth Division Captain/@comment-8589859-20130423081917/@comment-8295743-20130501020926

Sen, it was specifically stated no one in Soul Society apart from the Old Man knew about Sasakibe being able to use Bankai. That power, as seen, was quite large and could be easily seen by many people. What are the odds that in 200 years of training that no one could have seen Saskibe using that level of power? If he had been using it, it was obviously somewhere that no one could detect it. Otherwise, they wouldn't have stated that only Yamamoto knew about it.