User blog comment:Zwann/Vasto Lordes in the Espada/@comment-949252-20091119094341

Than why did Aizen ordered the top 4(Starrk,Barragan,Halibel,Ulqiuorra) not to unleash their resurrecion in Las Noches? all top 4 retain human shape (i do not know about Yammi) and most people have already seen their destructive power. Another point is their vast spiritual power. Ishida commented that "It feels like there is an ocean above the sky..." during the Ulqiurra vs Ichigo round 2 fight. If the top 3 contains anyone with a smaller amount of reiatsu there would be not point in making them the top 4. An adjuchas would most likely to be on captain level while it takes more than two captain-class fighter to bring down one of the top 4.

Starrk vs Shunsui,Ukitake(tempo.),Rose(tempo.),Love(tempo.) Barragan vs Soi Fon,Hacchi and Marechiyo(tempo.) Halibel vs HItsugaya,Lisa,Hiyori(all temporary,as she got incap/killed by Aizen) Ulqiurra vs Ichigo+Hollow Ichigo

The new Hollow form is considered to be hollow ichigo and it already has above-captain-class fighting capacity.