Board Thread:Questions and Answers/@comment-10797017-20130627100621/@comment-11051098-20140313152540

Regarding Unohana due to her healing skills - if this would be true, I would rather think it's Kirinji. He's been implied to have far greater healing skills than Unohana, although he apparently need his 2 hot springs for the job.

The 5 Royal Guards are stronger than the Gotei 13, so I find it strange if one of them is not on the list. Kirinji and Nimaiya are the greatest healer and the creator of Zanpakutô - one of them could very well be on the list.