User blog comment:Xilinoc/Ch. 605 - Don't Call My Name/@comment-5693502-20141113174043/@comment-1268838-20141114003238

Shunsui did not necessarily know about Gremmy in particular; he just knew that the Wandenreich was more powerful than any enemy they have ever faced before. He just so happened to know exactly how to tap into his full potential. It was a calculated risk, but as far as raw power goes, I suspect that Kenpachi is more powerful than Unohana and his pre-Muken self combined. And as Aizen once said, raw power is all that really matters when it comes right down to it.

At any rate, I somehow doubt that the Central 46 would release Aizen just like that. But if Shunsui's previous meeting with them is anything to go by, his nonchalance has its way of pushing them around. This is still a huge assumption of course.