Substitutes carry the sharpest workload nobody tracks

A player who comes on for twenty minutes runs at an intensity per minute no starter reaches, and the season plan ignores it.

The squad workload conversation is almost entirely about starters. Minutes played, matches in a window, days between fixtures. It is a reasonable place to start and it misses the group taking the strangest physical punishment in the sport.

Consider what a substitute winger actually does. He warms up in the first half, cools down, warms up again, cools again, and then enters a match in the seventieth minute with instructions to run at a tired full back. For the next twenty minutes he produces sprints at a density no starter can sustain, because he does not have to sustain it. His total distance for the day looks trivial. His high-speed distance per minute on the pitch is the highest number on the sheet.

Now do that for five weeks. The totals stay low, the flags never go up, and one afternoon he pulls up chasing a ball he has chased a thousand times. The staff look at the load data and see a player who has barely played.

The mechanism is not mysterious. Soft tissue injuries are associated with high-speed exposure and with sudden increases in it, and the substitute pattern is a sequence of sudden increases separated by very little accumulation. That is close to the worst structure you could design deliberately. The starter's body is at least chronically adapted to running fast because it does so every week for an hour. The substitute is asked to sprint cold, repeatedly, from a base that keeps eroding between appearances.

Five substitutions made this a bigger population rather than a smaller one. More players now live in the fifteen to thirty minute band, and more of them live there for months at a stretch, which is a fairly recent change to how a football squad is used and I do not think the physical planning has caught up with it.

The remedy is unglamorous and clubs already know it. Top-up conditioning after a short appearance, on the same day, before the body cools. Protected high-speed exposure in the week for anybody who has not started. The obstacle is not knowledge. It is that a player who has just sat on a bench for seventy minutes and then sprinted for twenty is in no mood to be told to go and run, and that the coach wants him fresh for Wednesday.

So the extra session gets skipped. Then somebody tears a hamstring in the seventy-ninth minute and it goes down as bad luck.