Just to have a bit of a nerdgasm as an aside for a moment, round robin tournaments with n teams are represented by complete graphs with n vertices.
i.e 15 round NRL competition would be represented by
where each vertex is a team and each edge is a match played between two teams. Each round consists of taking 8 edges from the above graph, where no vertex can be used twice, i.e no adjacent edges. There is a theorem that say this is possible to do 15x and then you'll have accounted for every edge in this type of graph.
That's how they do the basics of match scheduling. Awesome, no?