User blog comment:Xilinoc/Ch. 597 - Winded by the Shadow/@comment-24384892-20140918224717/@comment-24384892-20140918225309

Also, I don't think this is the first time we've seen Niansol (Sternritter W). I think he made an appearance way back in chapter 499. He might be that unidentified Sternritter that Ukitake was facing way back in that chapter.