User blog comment:Xilinoc/Ch. 668 - BIGGER,FASTER,STRONGER/@comment-1338810-20160331153730

Plot twist: Yachiru is the spirit of the eyepatch. :p Or Zaraki is so ridiculously powerful that, a la Gremmy, his reiatsu created an imaginary friend who is as strong as a lieutenant of the Gotei 13 and that everyone could see.