User blog comment:Salubri/Aizen, Yamamoto and Wonderweiss/@comment-1337270-20100225131740

I dont think that WW is there to defeat Yamamoto but to stop him from using his zanpakutou. Think of the Amagi arc. He used the Bakuto to stop Yamamoto form using his zanpakuto so he could defeat him. I think Aizen did exactly the same. He wanted to give him self a fighting chance and the only way to do that was to extinguish Rujinjakka. At least that was my take on it.