The final ten minutes with a one-goal lead is a distinct phase with its own rules. Teams that manage it well make deliberate changes rather than simply defending harder.
Dropping too deep invites the pressure
The instinctive response is to retreat towards the penalty area, which shortens the distance opponents must cover and concentrates play in the most dangerous zone.
A defence sitting on the edge of its own box also has nowhere to clear to, since the forwards are too far away to hold the ball.
The result is a cycle of clearances returning immediately, and every repetition is another chance for a deflection or a set piece.
Keeping a forward high is a defensive measure
An attacker positioned on the last defender obliges the opposition to leave at least one player back, reducing the number committed forward.
He also gives clearances a destination, so the ball can be sent somewhere useful rather than straight back into the contested area.
Substituting the last striker for an extra defender therefore often makes a team more likely to concede, not less, because the pressure never breaks.
The game is managed in seconds as much as in metres
Throw-ins, goal kicks and substitutions all consume time, and a team protecting a lead uses each of them fully within what officials permit.
Added time is calculated against these delays, so the gain is smaller than it appears, but the interruptions also break the opponent's rhythm and momentum.
The more useful version is retaining the ball in the corner, which removes time and possession simultaneously and forces the opponent to commit a foul or a defender.
Set pieces are where narrow leads are lost
A team defending deep concedes corners and free kicks at a higher rate, and those restarts allow the opponent to bring defenders and a goalkeeper forward.
Fatigue makes marking assignments break down at exactly the point when concentration matters most.
Coaches address this by simplifying the marking scheme late in matches, accepting a less sophisticated structure that tired players can execute reliably.
Substitutions should reinforce the plan, not just the numbers
Fresh legs matter most in the positions that cover the widest areas, which is why full-backs and wide midfielders are the most commonly replaced late.
Introducing a defender without adjusting the shape leaves the team with an unfamiliar structure at the moment it most needs certainty.
The safer approach is a like-for-like change into a shape the players have practised, keeping the arrangement stable while restoring the running capacity that holds it together.