Rivalries are not manufactured by marketing departments, though plenty have tried. The ones that last share three things.
The first is proximity. Not necessarily geography, though derbies built on a shared city are the purest form. Proximity can also mean two teams occupying the same competitive space for long enough that every season becomes a direct comparison. Without repeated contact there is no accumulation, and accumulation is what separates a rivalry from a good fixture.
The second is stakes. A rivalry needs matches that decided something — a title, a final, a relegation. Fixtures that mattered become the reference points supporters argue about for decades, and each new meeting is played partly against that memory.
The third, and the least comfortable, is grievance. Almost every great rivalry contains an incident one side has never forgiven: a refereeing decision, a transfer, a challenge, a celebration. Grievance is what gives a rivalry its emotional charge, and it is precisely the element that cannot be planned.
What is striking is how sport-agnostic this is. The same three ingredients explain a college football rivalry, two heavyweight boxers who split a pair of fights, and a pair of Formula 1 drivers in the same garage. Teammates, in fact, make some of the best rivals, because proximity is total and the grievance is unavoidable.
What rivalries do not require is balance. Lopsided records fuel plenty of them — resentment is a perfectly good engine.