I'd argue that SS, or OF, are their deepest positions in the minors.
I'm fine with a short-term solution. And, while unpopular, I'm also fine with Polanco as that short-term solution.
I'm more concerned about a Plan B at catcher. Jeffers is young and could go either way. Not sold on Garver's long-term success. And he had a gruesome injury last year (which can't help). There are a million stopgaps at SS. There are only AAAA level stopgaps at C.