User blog comment:Xilinoc/Ch. 566 (not out yet, but dis gon b gud)/@comment-26420452-20140202184043/@comment-10554972-20140202185814

I think you're taking the "impossible to defeat a Sternritter without a Bankai" too seriously. Kenpachi defeated a few without Bankai, and Yamamoto killed the Overkill without using his. Renji was almost capable of killing Mask with his Shikai. The only reason he didn't was because Mask was able to heal from his wounds and got ridiculously powerful from the audience. It can be done, it's just that the Sternritter are really strong. Rukia has trained with the Royal Guard, so she's gotten a lot stronger, and has possibly perfected her Shikai. I would say that she would be capable of winning without Bankai.