The move to five permitted substitutions in many competitions changed formation planning more than it changed squad rotation. A shape no longer has to last ninety minutes.
Three changes forced conservatism
With three substitutions, one was usually held back for an injury and another spent on a tired forward. That left a single genuinely tactical change.
A coach therefore picked a shape that could survive the whole match, since there was no realistic way to convert it into a different one. Flexibility had to be built into the starting eleven.
The common solution was players who covered two roles, allowing a shape change without a substitution. Versatility was the substitute for substitutions.
Five changes make a second shape affordable
With five available, a coach can make a double change that alters the structure, not just the personnel. Two players arriving together can convert a back four into a back three.
That turns the starting formation into a first phase rather than an identity. Its job is to handle the opening hour under the conditions expected then.
Coaches now plan the successor shape before kickoff, with the players for it identified. The bench is selected to enable a specific transformation.
The windows are the real limit
Substitutions must generally be made within a limited number of stoppages, which means changes cluster rather than spreading evenly. A coach cannot make five separate adjustments.
This encourages the double and triple change, since using a window on one player wastes its capacity. Changes are batched by design.
The batching pushes toward structural changes rather than like-for-like swaps. If three players are arriving at once, the shape may as well change.
Starting shapes became more specialized
Because a formation only needs to work for an hour, coaches select more aggressively for the specific opponent. A shape that would be unsustainable across a match is viable for sixty minutes.
High pressing structures benefit most, since their main weakness is that they cannot be maintained. Fresh legs arriving at the hour extend the phase.
The result is matches with two distinct tactical periods rather than one continuous game. Analysis that averages across the match blurs them together.
Depth became a tactical asset
The advantage of five changes is only available to squads with five players worth introducing. Teams with thin benches gained little from the rule.
In leagues with tight budget structures this widens the gap between well-constructed and poorly constructed rosters. The rule rewards squad building.
It also changes what a bench player is for. The role is no longer covering absence but executing the planned second shape.