User blog comment:Xilinoc/Ch. 665 - The Princess Dissection/@comment-5693502-20160310143820/@comment-5551986-20160312013027

His shikai probably restructures his reiatsu to suit different tasks. Whereas his bankai restructures whatever it touches. His shikai can only do his reiatsu or reiryoku changing it to shields, blasts, nets, bombs, razor blades etc.