The problem here is that Greek is an inflected language (like Latin - I dunno about Aramaic, NYer?) with gender, neither of which occur in English. Sentence structure in English fills the function that inflection performs in Greek. So word order doesn't matter in Greek, and you're wasting your time diagramming sentences. Everybody (at least everybody who can read Greek) knows the position and function of each word without bothering to diagram anything.
If sentence diagramming doesnt work just because of a translation, then the translation is in error
subjects and predictes and verbs and nouns are all arranged after translations, and the verse can then be diagrammed
and that means Peter is not the Rock, what Peter spoke told us what the ROCK is, not Peter.