User blog comment:General MGD 109/Ranking of existance/@comment-3481504-20120226021740/@comment-3481504-20120226192601

If not Cas, at least Uriel could overpower Alastair, given that he easily overpowered two demons at once, as demonstrated in "Heaven and Hell".

Besides, Alastair adamantly admitted that he doesn't know how to kill angels, therefore Cas has the upper-hand, if you will.

Even if he did send Cas back to Heaven, he'd just return in his vessel moments after, and defeat Alastair.