User blog comment:CoolJazzman/Why do you think Yamamoto wasn't giving a promoted to become a royal guard./@comment-8295743-20130417035134/@comment-6904925-20130417130614

Like SenNoKuroiHonoo said about Aizen, Ywach took drastic measures against him too, he had someone impersonate him, thus wasting much of strength, plus he had that plate that could steal his bankai, if Yamamoto fight with Loyd showed one thing (besides his bankai's power) was what would happen if Ywach couldn't steal his bankai.

Although I do agree with you that Yamamoto was probably stronger when he was younger.