From time to time, Europe's Champions League throws up shocks, such as Tottenham's dramatic run to this year's final or Liverpool's amazing comeback to eliminate Barcelona on Tuesday.
In general, though, there is a large dose of predictability. The major honours are shared around a select group of clubs.
In South America's Copa Libertadores, meanwhile, things are more fluid. No one has managed to retain the title since 2001. Successful teams are always being broken up, opening space for rivals to get their hands on the silverware. So, if the Champions League has the quality, the Libertadores has more shock potential.
This year's group phase, however, has been low on early casualties. There were some scares, particularly for the past two winners. Reigning champions River Plate of Argentina did not manage a win in the first three of their six group games, then hauled themselves to safety. And 2017 winners Gremio of Brazil were in a worse pickle, with just a single point from their opening three matches, but three impressive wins saw them comfortably over the line.
Of the 16 teams who go into the knockout phase, 11 are former champions. Only two ex-winners have fallen by the wayside -- the lowest number since 2013, when Penarol of Uruguay were the only giants to suffer an early exit.
And Penarol have done it again. They have failed to make the cut in a repeat of last year, of the year before that and the year before that. And then add some. This is the seventh consecutive time that the Montevideo side have not made it out of the group phase and into the final 16. And measured against the greatness of the club's tradition, this has to hurt.
Back in 1960, Penarol were the first champions of the Libertadores. They did it again in 1961 -- and then beat an excellent Benfica side to proclaim themselves world champions. There was a repeat job in 1966, when winning the Libertadores was a prelude to beating Real Madrid home and away. In all, they have five Libertadores titles. But the last one was in 1987. Since then, a run to the 2011 final is the only time they have come close. More often than not, Penarol have been condemned to humiliating early exits. And there is very little they can do about it.
The big change in the club's fortunes represents the rise of television as the most important element in football finances. In a pre-television age, a club's market was largely restricted to the thousands of people in the stadium. At that point, Penarol -- and their great local rivals Nacional -- could compete with anyone in the world. They had a magnificent tradition of producing players, and they could also buy in from abroad. One of the great Libertadores legends is Alberto Spencer, centre forward of Penarol's all-conquering 1960s side. He came from Ecuador.
Nowadays, of course, a player of his outstanding quality would be whisked away to Europe at an early age -- as happens with the best products of Uruguayan youth football. With the advent of television, the market was no longer restricted to those in the stadium. There was a potential worldwide audience of billions. And with Uruguay having a population of little more than 3 million, the country's clubs could no longer compete on a level playing field.
This year was especially cruel for Penarol. They were drawn in the only group containing three former champions. With only two places available in the knockout phase, there was not space for everyone. And the Uruguayans finished with the same record as Flamengo of Brazil and LDU of Ecuador with three wins, a draw and two defeats. In any other group, 10 points would have been enough to make progress. But in the case of Penarol, they were eliminated on goal difference.
In their last group game on Wednesday, they had to win at home to Flamengo, a giant with far greater resources who have been through their share of group phase Libertadores traumas. With all the tension on the field, it was an occasion almost guaranteed to generate more heat than light. Penarol took some risks, left themselves open to the counterattack and had some 25 minutes against 10 men when Flamengo right-back Para was sent off. But the breakthrough never came, the match finished goalless and Penarol went out.
The Uruguayans have shown progress in the 11 months since former international centre-back Diego Lopez took over as coach. The problem is, though, that it will be difficult to build on this promise. Talented youngsters such as Braian Rodriguez, Darwin Nunez and Agustin Canobbio might have moved on before next year's campaign, assuming that Penarol qualify. Grizzled veterans such as Cristian Rodriguez and Walter Gargano will be a year older. The blend that nearly got them into the last 16 this year might not be present in 2020.
Penarol, though, can look back on their campaign this year with much more pleasure than the other former champion to fall early. Atletico Mineiro of Brazil, 2013 winners, had no chance even before taking the field for their final game. A total of 10 goals conceded in six matches tells its own story -- one which will not come as a surprise to those who followed last year's Brazilian Championship. Atletico had a poor defensive record and qualified for the Libertadores as a result of finishing 6th in the league -- an argument, perhaps, for the view that there might now be too many Brazilian clubs in the competition.
There are plenty left in the last 16, though. Brazil have six teams, Argentina have four and Paraguay have three, Ecuador have two and Uruguay have one.
The knockout phase will not get underway until July, but the draw takes place on Monday. The group winners will take on the runners-up. Until almost the last kick of the round, it seemed that only teams from Brazil and Paraguay would finish top of the groups. But then Carlos Tevez scored a match winner for Boca Juniors. And as a result of topping their group, Boca now have a one in eight chance of meeting River Plate in the next round in a rematch of last year's infamous and controversial final match.
Group winners:
Cruzeiro, Flamengo, Internacional, Palmeiras (Brazil), Cerro Porteno, Libertad, Olimpia (Paraguay), Boca Juniors (Argentina).
Runners-up:
Godoy Cruz, River Plate, San Lorenzo (Argentina), Athletico PR, Gremio (Brazil), Emelec, LDU (Ecuador), Nacional (Uruguay)