This page is an outgrowth of my big list at User:Le Deluge/categories. As you'll see there, I had to grab a lot of red-listed categories for something else I was working on, and I ended up with a list of around 6500 (still only a fraction of the total, I will do the full list at some point) red-link categories that need either creating or editing the articles that point to them. I cleaned up over 1500 of them to get rid of most of the obvious typos, spam etc, but that still left nearly 5000 categories to create. So I need some help.
I've run some filters on the list to generate the following, and hand-curated them to get rid of the obvious gridiron/rugby/Gaelic/Aussie Rules categories, but there's bound to be some left behind, for which apologies. Conversely there will be footy categories (particularly "team" categories) still lurking in the main list, and feel free to have a quick look over that. But the 521 categories here will give you something to keep busy with!
I've split them into "managers", "seasons", "players" (with a few parent club categories mixed in) and "the rest". There's a bit of an art to creating these categories, first of all you have to look at the link and see if it's spelt correctly, in the correct format for Wikipedia (for instance, "Category:Torino players" should be "Category:Torino F.C. players") and matching the main article name. If not, you will have to edit appropriately any articles that point to it.
To help you I've derived a potential club category and article and put them after each player/season category, which will allow you to quickly check what the parent hierarchy looks like. If there is already a blue-linked matching club category, you can be fairly sure that the proposed fooian category is correct. If there is a blue-linked club article but the club category is red-linked, then it's probably just a case of the club article needing creating, but you should check that the blue-link article isn't just a redirect to a different spelling.
Then it's a good idea to look at the equivalent category of a big club ideally from the same country (eg Category:Real Madrid C.F. players or Category:Manchester United F.C. seasons - typically there will be a {{catmain}} link and some other bits in the header, plus at least the club category and a Category:Fooians in country by club. You can then use that as "inspiration" for the new category.
Anyway, enough talking, here are the categories!!