Two systems will tell your club two different numbers for the same run

Optical tracking and wearable devices disagree about the same player in the same match, and nobody publishes the gap.

A club signs a midfielder partly because his high-speed distance is outstanding. He arrives, is fitted with the new club's kit, and turns out to be ordinary. Nobody lied. The two clubs were using different tracking systems.

This happens more often than the industry admits. Optical systems track players from fixed cameras and infer position from image data. Wearable devices sit between the shoulder blades and report their own position from satellites plus an inertial unit. Both produce a stream of coordinates, and both then apply filtering to smooth the noise before they compute speed and acceleration from it. The filtering is where the disagreement lives, because how aggressively you smooth determines how much of a sudden change of direction survives into the output.

Add threshold choices on top. One provider counts a sprint above one speed, another above a different one, a third defines high-intensity relative to a player's own maximum rather than an absolute figure. All three approaches are defensible. None of them are comparable. So a player's numbers can shift by a meaningful margin the day he changes club, or the day his club changes supplier, and the shift has nothing to do with him.

The consequence I find genuinely worrying is the medical one. Return-to-play decisions increasingly reference load thresholds, and those thresholds were derived from data collected on a specific system. Port the number to a different one and the threshold means something else. A physio comparing a rehabilitating player's current output against a baseline recorded on the old provider is comparing two different measurements and calling it progress.

The fix is boring and achievable. Publish the method. State the sampling rate, the filter, the thresholds, and run a period of parallel collection whenever a club switches supplier so that the offset is known rather than guessed. Some clubs do this. Most do not, because it costs money to run two systems for a month and nobody in the building is arguing for it.

Meanwhile the numbers keep leaking into public analysis, where they get compared across leagues as though they were temperatures.

Distance is not a measurement. It is the output of somebody's algorithm, and you are allowed to ask whose.