User blog comment:Godisme/San'ou/@comment-1920550-20120726161308/@comment-4484409-20120729191948

There would be no point in the Vizards fighting the Gotei 13. They would lose even if they are hybrids and the Gotei 13 wasn't their real enemy anyway. It was Aizen, Gin, and Tosen. Besides why would they want to fight former comrades in a pointless battle that's not even their fault? The Arrancar, the few there were before Aizen came, would also lose if they just attacked the Gotei 13. They were fine in Hueco Mundo, at least Barragan was, and had no reason to attack the Gotei 13 or even leave. The reason that the Gotei 13 are so powerful and have always been on top is because they are really the only ones that are a large military organization trained in combat. The Arrancar had no cohesiveness or sense of unity since their world is a vicious and cannibalistic jungle, so to speak. The Vizards are too small a group and it would make no sense to fight them.