Soccer leagues with relegation are usually pretty straightforward. Bottom three go down, top three go up.
But as you move down the pyramid, at some point leagues become regionalised. Now you have to find a way to determine which of 40, or 60 or 80 teams are promoted to the next division. This problem occurs in Spain where the second division meets the third, and they have developed a pretty good system of resolving it.
Let's start at the top. Spain's Primera Division has 20 teams. The bottom three are relegated. Next is the Segunda Division. The bottom 4 of 22 teams are relegated there.
But in the next division down, the Segunda Division B, there are fully 80 teams, 20 in each of four regionalised groups. How do we find the four teams to be promoted?
One way, of course would simply be to promote the winner of each group. There are two drawbacks to that. First, the groups may not be evenly balanced, so an outstanding second-place team may be passed over for a mediocre first-place team. And second, with only the winner promoted, many teams in each group would be virtually eliminated from the race by halfway through the season, leaving them little to play for.
Instead Spain has a post-season playoff system that seems to work quite well. Four teams from each group make the playoffs. Each is seeded based on its finishing position within its group, so there are four 1's, four 2's, four 3's and four 4's. The teams are then paired in two-game total goal series as follows: the 1's are drawn against each other, as are the 3's, while the 2's face the 4's.
That may seem counter-intuitive, but see how it works. The two matchups involving 1's are direct qualifiers. The two winners are immediately promoted. And the two losers are not eliminated. They join the six winners of the 2-4 and 3-3 matches in another playoff. These eight teams are winnowed by two more home-and-home rounds, and the two survivors are promoted as well. (Readers may note some similarities here with Australian playoff systems.)
This system cleverly serves the two fundamental goals of sports structuring, which are often in opposition: rewarding the best teams and giving as many teams as possible a chance. Fair and exciting.
Notice that the four group winners still have a huge advantage: they get one free shot at promotion, and even if they lose they can be promoted with two straight series wins. By contrast, the second, third and fourth place teams must win three straight series with no second chance. Still, they have a chance.
Few neutrals get excited about the results of a nation's third division. But FRB will have at least one eye on the Spanish Segunda B playoffs this spring.