RT9

The sheer number of Hollows summoned by the bait, what Uryu brought down on Karakura was not enough for any one Captain to deal with. Or two for that matter. It would take a squad of trained professionals to deal with the majority of the Hollows off-screen. A squad of Captain-class Shinigami capable of moving quickly and efficiently in a sizable group – Moreover, they would have to be beaten without garnering the attention of the Soul Society or Aizen, so they would need to defeat most of these Hollows with abilities the Soul Society could not necessarily track.