Easy - if Buxton finds out from this specialist that season ending surgery is the best option, you end his season, put him on the 60 day DL, and add Kiriloff to the 40 man.
That would get Kirilloff on the 40-man, but would not make him postseason eligible. And unfortunately, we couldn't petition to replace Buxton on the postseason eligible list then until Buxton spent a full 60 days on the IL.
We still have Gordon on the AAA IL who we could petition to replace, but we might have designs on using his spot to make Miller or Graterol eligible.
Otherwise, we could instead put Buxton on the 10-day IL so we can petition to replace him, and then find another way to open a 40-man spot (i.e. DFA'ing LaMarre or Diplan).
Although I'm guessing the idea of a Kirilloff call-up is unlikely, in any case!