This element is the most complex of the four. Basically, this element says that if you could have realistically purchased or licensed the copyrighted work, that availability weighs against a finding of fair use.

This impact is also closely linked to purpose. If your purpose is commercial (which can be argued due to its use on a .com website), then an adverse market impact will be easier to prove than if the work was quoted in a research paper.

Bottom line

Don't use any more than a quotation or single paragraph at the most when curating content. Even a couple of paragraphs in a short original work could run afoul of "fair use." It's just more simple to rewrite things in your own words rather than copy/pasting.