[I_teach_writing]

Foucault was primarily interested in how language and institutions created relations of power among "subjects," who have very little agency or free will in the face of webs of power, and the relations that surround them.

The most direct relationship I know of Nietzche to post-structuralism runs through Derrida, a French philosopher writing at the same time as Foucault. Both Derrida and Nietzche were interested in the Greek Sophists, who were rhetoricians who believed that language didn't exactly have the ability to access "Truth."

There is likely a direct connection between Foucault and Nietzsche, but my Foucault isn't as good as my Derrida. But if I recall correctly, what is common to both is the pessimism =)