You get countered in the minutes after your own changes

Rest defence is an agreement between specific players, and a substitution deletes it while the shape looks unchanged.

Go back through the goals your team conceded on the break this season and write down the clock beside each one. My bet is that a suspicious number landed within four minutes of your own substitution, and that nobody in the debrief mentioned the substitution at all.

Rest defence is not a shape. It is an agreement. Who covers when the winger goes, who may gamble on the loose ball, who screens the first pass out, who sprints and who holds position. Almost none of that exists on a tactics board in any useful form. It gets built over months by the particular players who keep standing next to each other, and most of it is never said out loud. Then you change two of them at once and the agreement is gone, while the formation graphic on the broadcast shows the same numbers in the same places.

The new man makes it worse, through no fault of his own. He has been sitting for an hour, he has been told to change the game, and the first thing he does is get forward. That is exactly what he came on to do. Meanwhile the player who stayed on keeps the reflexes of the pairing that just walked off, covering for a runner who is no longer running and stepping across to help a man who is now sitting down.

A few unglamorous suggestions follow. Make changes in pairs who already play together, rather than one at a time down opposite flanks. Take the dead ball instead of the live one, even if waiting ninety seconds makes the manager look slow, because you cannot brief anybody while the ball is in play. And stop changing a winger while leaving the full back behind him, which is the most common way in football to hand a man an unfamiliar partner in the exact area where a counter begins.

There is a harder version of this claim. The fifth substitute has made the problem worse rather than better. More changes means more of these windows, and clubs treat them as free because fresh legs show up in the running data and disorganisation does not.

The scoreboard blames the man who lost possession. The change that removed his cover happened three minutes earlier.