South Australia was previously represented in the now defunct National Soccer League by Adelaide City and West Adelaide , who have historically faced off in the Adelaide derby. The Federation Cup is a knock-out competition for South Australian clubs. Since The winner of this competition plays off against the winners of the NPL conferences from other states in a national finals series to determine the NPL Champion. From Wikipedia, the free encyclopedia. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.