User blog comment:Uraharattack/Grimmjow or Gantenbainne? Maybe both?/@comment-10554972-20130730025528

Grimmjow is almost certain for the one who was with Urahara when he SoulSkyped Ichigo, due to the hostility he showed when he heard Ichigo's voice. I don't think Ichigo would know the voice of any others in Hueco Mundo that he would consider dangerous. Also, it couldn't have been Gatenbainne who killed Quilge, as that person had a sword, and Gatenbainne's sealed Zanpakuto wasn't a sword. But we saw two people with Chad, so while one of them is probably Grimmjow, the other could potentially be Gatenbainne. I think that is a fairly good guess. Plus, there might be more that we just haven't seen, Fraccion is almost certain, but I would love to see Ashido again. Kubo initially wanted him to be in it, but didn't have time, so he became non canon anime. I think it's possible he becomes canon now, but it's probably unlikely.