User blog comment:SenNoKuroiHonoo/Aizen's defeat- caused by Ichigo or his will?/@comment-2226235-20130401191210/@comment-5112778-20130404090608

And also how he place Starrk as the Primera Espada.

Maybe, just maybe, Aizen feels sympathy for him and he sees similarities that Starrk has with him, large amounts of power, yet no one around him that is able to be as strong as him.