What is it with South American cup competitions? FRB has written about their odd structures on a couple of occasions. Let's add Chile to the list.
In 2010, the Copa Chile was a standard knockout tournament. But for 2011, quite a strange system has been put in place.
The first few rounds, involving lower division teams, are ordinary two-legged playoffs. Eventually, 18 lower-division sides advance to a group stage, where they are joined by the 18 teams from the top division.
So, 36 is a nice even number for a competition. There are lots of fairly straightforward ways of winnowing a field of 36 teams down to one champion. This is not one of them.
First, the 36 teams are classified into three merit-based groups. Group A is the top 12 from the Premier League. Group B is the rest of the Premier League and the best 6 lower division sides. The weakest teams make up Group C.
Each team is then assigned three opponents, one from each group, and plays home and home against each of them for a total of six matches. The opponents are chosen with geography in mind, so that there as many local rivalries as possible.
The weird thing is that all 36 teams are placed in one jumbo table; the top 8 of 36 advance to the quarterfinals, based on their performance in those six games. That's a whole lot of teams for a single table.
It's also seems a bit unfair that teams are being ranked based on only six games, when every side plays a different set of teams. In the Champions League, for example, teams play a six-game group stage, but are compared only against teams that have played the same opponents as they have.
For practical purposes, the Chilean Cup's ranking is really going to be based on fewer than six games. The top teams, who will be the main contenders for the eight slots, will win pretty much all their games against "B" and "C" teams. So the eight winners will essentially be chosen based on the results of two games, again with each team playing a different opponent. And the tie breaker, which is almost certain to come into play, is goal differential. So expect to see A teams running it up on B's and C's.
After this strange round, the tournament returns to classic quarters, semis, and finals. You kind of have to wonder if they couldn't have arranged a more conventional group stage as well.