I don't know that it's really necessary. I had seen the previous Creed film, but didn't really remember much about it except that I liked it. If you've ever seen Rocky IV, that's probably the one that's referenced the most. If you haven't seen it, a brief skim through the Wikipedia entry for...
I saw this tonight and was pleasantly surprised. I liked it much more than I expected to. While it follows the typical Rocky formula, there's enough side-story to keep things interesting and fun. It does drag a bit during the middle of the film, but overall a good time.