Europe's leading club competition abandoned small groups in favour of one large table in which clubs play a selection of different opponents. The change was driven by dead fixtures and by the demand for more high-value matches.
Groups of four produced dead matches
In a four-team group with six matches, qualification was frequently decided before the final round. Teams then played fixtures that could not change anything.
Broadcasters were selling those matches, and clubs were fielding weakened sides in them, which damaged the value of the product at exactly the point it should peak.
The structure also produced repetition, since each club met the same three opponents twice within a few months. Familiarity dulled the novelty that gives continental football its appeal.
One table keeps outcomes uncertain for longer
With every club ranked in a single standing, a result anywhere in the competition can move a club's position. There is no isolated group whose fate is already sealed.
Because qualification and seeding depend on the whole table, the final round of matches matters to almost every participant simultaneously.
Playing all remaining fixtures at the same time removes the advantage of knowing what a rival has already done. Every club goes into the last night with the same information.
Varied opponents replace repetition
Each club faces a set of different opponents drawn from ranked pots rather than meeting the same three twice, which spreads matches between clubs that rarely met.
The draw is constrained so each club encounters a comparable spread of strong and weak opponents, keeping the single table broadly fair.
Not every club plays the same opponents, so strength of schedule varies, and that is the main criticism the format attracts. Two clubs on identical points may have faced very unequal fixtures.
More matches means more inventory
The format increases the number of fixtures played in the early phase, which increases the number of matches available to broadcasters.
That was a central objective, since the competition's revenue depends on selling a larger volume of meaningful games rather than a small number of showcase ties.
It also allows a larger field to take part while still producing a credible ranking of who progresses.
The cost is a heavier calendar
Additional fixtures fall on clubs already playing domestic leagues and cups, and they fall on the players with the longest seasons.
An intermediate knockout round for clubs finishing in the middle of the table adds two more matches for those who do not qualify directly.
The tension between selling more matches and protecting player workload is unresolved, and it is the fault line along which the format will be argued over next.
