The Old Group Stage Format:
In the first edition (1992-1993), the tournament consisted of 8 teams after a qualification phase. The eight teams were playing in two groups followed by a final between the group winners. The first season included a total of 36 participating clubs in the qualification, since then the numbers had increased.
In the third edition of the Champions League (1994-1995), the tournament expanded to 16 teams (excluding the qualification). The format consisted of a group phase with four groups followed by three knockout stages.
In the 1997 - 1998 season another expansion added more teams to 24 (excluding the qualification). A group phase which included six groups, was followed by a knockout phase in three stages.
In the 1999 - 2000 season the tournament expanded for the third time and would now include 32 teams (excluding the qualification). The teams were divided into eight groups and the first group stage was followed by a second, and finally a knockout stage.
In the 2014 - 2015 season 2014-2015, the second group stage was abandoned. Instead, another stage (Round of 16) in the knockout phase was played.
The New Swiss Model Format:
Starting from August 2024, the European tournament features a completely new format designed to get more high-pressure, high-profile games to replace the few meaningless matches some teams play at the end of the group stage.
In the new Swiss Model format, all 36 group stage (now referred to as the "league stage") participants are organized into one massive table. The teams play eight matches against other teams of varying difficulty, collecting the traditional three points for a win and one point for a draw.
The fixtures are determined by a draw in which the 36 league stage participants are organized into four pots of nine clubs each, with every club playing matches against two other teams from each pot.
At the end of the eight rounds, the top eight teams in the table qualify for the round of 16 directly, while clubs in positions 9-24 will be drawn into a two-legged playoff round.
The winners of the playoff round matchups advance to the round of 16, while the losers drop out of Europe entirely.
From there, the traditional single-elimination style returns and the 16-team knockout bracket takes over. In summary, the current European format is made up of the following:
- a 36-team single table league phase
- 8 matches are played against 2 teams from each of the 4 pots
- the top eight teams advance to Champions League Round of 16
- the 9th through to 24th placed teams advance to a two-legged playoff round
- the 8 playoff winners advance to Champions League Round of 16, the losers drop to the Europa League
Reasons why the current format does not work and why it is better to go back to the old format :
First, it provides more matches, and more matches mean more broadcast revenue but at the risk of the players health being jeopardized. In order words, this change is money driven with potential concerns of corruption taking place at the higher levels of football management. In the traditional group stage format, the 32 teams play 96 games before half the field is eliminated.
In the current Swiss Model, the 36 teams combine to play 144 matches throughout the league phase, with 16 more games in the knockout playoff round, bulging the current fixture list by 64 games, an enormous increase of 66.7% on the old format.
In total, the tournament has doubled in size from front to back, jumping from 125 to 225 games year-over-year. The huge increase in matches puts further strain on clubs, leagues, and players who are already stretched extremely thin from domestic league, cup and international competitions all adding matches.
Although the current Swiss format allows for additional slots for teams to qualify to the Champions League and it sees to it that more big clubs enter the competition. It achieves this objective by forcing clubs to prioritize reserving their top players to perform mostly at the top European Competition levels. This comes at the cost of managers and coaches choosing not to use such key players in important and tough domestic leagues and cup games in order for those players not to get injured. As a result, the significance and quality of domestic league and cup games drop drastically with each passing season.
Source Information: https://www.sportingnews.com/uk/football/news/swiss-model-champions-league-uefa-debut-ucl-format-group-stage/a2d1e16bb0f0d24b364d4db4
Source Information: https://www.footballhistory.org/tournament/champions-league.html