Expanding a World Cup is not simply a matter of inviting more teams. Tournament size determines group structure, and group structure determines how teams behave before the knockout rounds begin.
Why powers of two are convenient
A knockout bracket works cleanly when the number of qualifying teams is a power of two. Sixteen teams give four rounds, thirty-two give five, with no byes required.
Group stages must therefore deliver a qualifying field of that shape. The number of groups and the number advancing from each are chosen backwards from the bracket.
When the total entry does not cooperate, organisers either add a preliminary round or promote a set of best-placed teams from across the groups.
Groups of three and their weakness
Groups of three are the compact solution, since they deliver a large field with few matches per team. They also reproduce the collusion risk that simultaneous kick-offs were designed to remove.
In a three-team group, one side sits out the final round having already played. The two teams on the field know precisely what result suits them both.
There is no second match to run simultaneously, so the standard remedy is unavailable. That structural flaw is the main argument against the format.
Groups of four and the match count
Groups of four preserve simultaneous final fixtures and give each team three matches, which is a fairer sample and a more attractive product to sell.
The cost is volume. More groups of four means substantially more matches, which lengthens the tournament and increases the burden on venues, officials and the calendar.
A longer tournament also collides with domestic seasons, since players must be released for a period that grows with every additional round.
What best-placed qualification does
Advancing several third-placed teams keeps groups at four while filling a larger bracket. It also weakens the incentive to win a group outright.
Teams begin calculating against results in other groups they cannot influence, which makes the final round harder for spectators to follow and easier to manage cautiously.
Bracket construction becomes awkward as well, because which third-placed teams advance determines who meets whom, sometimes only after the last group match finishes.
The trade nobody escapes
Every expansion buys wider participation with either more matches, weaker group incentives, or a longer event. No structure delivers all three.
Participation has value beyond the pitch, since a nation qualifying for a first tournament sees investment and interest rise sharply at home.
The design question is therefore not whether expansion has costs but which cost the competition is willing to carry, and that answer changes with each cycle.
