To a human observer of football (the soccer sort), the on-pitch patterns—offence stretching and squeezing defence, counterattacks coalescing out of thin air—are as mesmerising as they are easy to follow. For an artificial-intelligence (AI) model, however, understanding what is going on is far from trivial. Raw video is stuffed with information, most of it irrelevant. The first thing an AI engineer, therefore, has to do is teach the model what matters and what doesn’t. For football tactics, player and ball positions are a good place to start. But a team isn’t just a collection of isolated players; it’s a network of relationships.