Using Breadcrumbs instead of Navigation Bar?

I was wondering what everyone’s thoughts were on using Breadcrumbs as the main navigation for a site and having no Navigation bar?

I have a client that is determined to use only breadcrumbs as the means for navigation on her site, and does not want any other navigation above it (she thinks it’s redundant, so her solution is to delete the Nav bar, instead of the Breadcrumbs). I cant seem to talk her out of it, or explain the necessity of a main navigation bar (that’s always/permanently on the page where people can easily find it).

Does anyone have tips or solutions, any references or articles to help me out? If anyone has an argument for or against this I would love to hear it. It would help me out considerably.

I greatly appreciate any and all feedback. Thank you