The vest data turns up in the contract meeting eventually

Monitoring gathered for player welfare rarely stays inside the medical room once a renewal is on the table.

Nobody signs a monitoring consent form expecting it to be read out across a negotiating table. It happens anyway, in softened language, and every senior professional knows it does.

The pitch to players is welfare. Wear the unit, let us see the loads, and we protect you from an overreaching week. That case is real. The problem is custody. The same output, aggregated across seasons, is a decline curve, and a decline curve is the single most useful document a club can hold when deciding whether to offer three years or one.

Clubs will say the data never leaves the performance department. Sometimes true. But the performance director reports to a sporting director who sits in the contract meeting, and the question asked is never show me the file. It is: are we comfortable with a three year deal for this player. The answer is informed by the file regardless of who reads it.

The asymmetry matters because the player has no equivalent. He cannot see the model, cannot see the comparison group, cannot commission an independent read of his own numbers, and in many leagues cannot take a full export of them to a rival club to argue the opposite case. Data portability is a live issue in every other industry and barely discussed in this one.

There is a market consequence too. A player whose internal metrics look poor may be quietly shopped while his public output is still strong, which is efficient for the selling club and corrosive for trust across the whole workforce. Squads talk. Once players believe the vest is a contract instrument, compliance drops, and the welfare case that justified the system collapses.

My preferred rule is dull and would work. Any monitoring data used in a contractual decision must be disclosed to the player and his representative on request, in a portable format, with the model that interpreted it. Not banned. Disclosed.

Clubs will argue that reveals proprietary methodology. Perhaps it does. It is still the player's body, measured on the player's time, and the only party in that room whose asset is genuinely non-transferable is him.