I recently found myself about to write "David, using a metaphor of Saul's, said…", with the intended meaning that Saul had coined the metaphor (rather than it being a metaphor involving Saul in some way).
As a native speaker of English (though not necessarily the Queen's) this came naturally to me, but then I had my doubts as to whether it is regarded as grammatically correct, and even if so, whether it would seem awkward to most readers.
In looking for examples and discussion of the issue, I found this:
“It’s an academic book,” Wolf said. “I’d like to think that a general
reader could read it kind of encyclopedically. You know, they go to
see a play of Shakespeare’s and what is ‘Hamlet’ really about? That
kind of thing."
This, however, is a direct quote of a spoken sentence, so I remain unsure as to whether this usage should be avoided other than in spoken English or in quoting someone's words.
Note that here, I am primarily interested in the grammatical and style take on this form of construction, rather than looking for alternative ways of phrasing it – I can do that myself – and nor am I seeking advice, though doubtless well-meaning, amounting to "I'm not sure, so you should avoid it", but by all means offer alternatives if they help illustrate your answer.
Best Answer
Your sentence is much better off as you started, though I would personally prefer not to separate the subject from the verb by too many words:
or
This double genitive here is very useful to avoid ambiguity. Although the idiomatic phrase is metaphor for something, many do use metaphor of in this sense. Even Wikipedia does:
So if you say, using a metaphor of Saul, those who are used to saying metaphor of might mistake it as meaning a metaphor, an image, a symbol for Saul, and not a metaphor that belonged to Saul.
M-W explains:
It's true, if there is no ambiguity, the double possessive is definitely redundant. BUT:
As a final addition, not so relevant to your question, I will quote a detail that M-W draws attention to in a way that manages to put a smile on your face while at the same time pointing once again to what I might call with admiration the indocility of this fascinating language to fixed grammar rules: