For decades an injured player just kept playing

Football refused substitutes until 1965 in England, and the reason it finally allowed them was not welfare.

A man pulls a hamstring in the twentieth minute. His side plays the remaining seventy with ten, or with him limping on a wing as a decoration, because the rules provide no remedy. Cup finals were decided this way. Whole seasons turned on it.

That was football until the middle of the 1960s in England, and later in plenty of other places.

The argument against substitutes was that they would be abused. A manager could claim an injury that did not exist in order to change a losing team, and since nobody could verify an injury from the touchline, the rule would collapse into tactical substitution, which was considered a different thing entirely and obviously unacceptable. The authorities were right about the prediction and wrong about the conclusion. Substitutes were introduced for injuries only, the pretence lasted about five minutes, and tactical changes were formally allowed soon afterwards because everybody was already making them.

What strikes me is the ordering. Welfare was not the winning argument. Fairness of the contest was: a match between eleven and ten is not the fixture anyone bought a ticket for, and cup competitions in particular were producing finals that were over as a contest by half time. The injured player's own interest, the fact that he was being asked to run on a torn muscle in front of a crowd because leaving would betray his team, was a secondary consideration at best.

You can see the same ordering in every later expansion. One substitute, then two, then three, then five, each step justified by fixture congestion and squad management rather than by the health of the individual. The concussion substitute is the first change I can think of that was argued primarily on medical grounds, and it took an enormous amount of external pressure and several very bad afternoons on television.

There is a real cost to the modern version, and I will grant it. Five substitutes favour deep squads, which means rich clubs, and a tired defence being run at by fresh legs is a less honest contest than it looks.

But the alternative was a game where the correct thing to do with a broken man was leave him on the pitch.