Half-space entries are counted by drawing lines that are not on the pitch

The zone that half of modern tactical analysis rests on has no agreed boundary, so every count of it is a house rule.

Nobody painted those lines. That is worth remembering before you quote the number.

Half-spaces are a genuinely useful idea. The vertical channels between the centre and the wing, where a receiver can face goal without being pinned to a touchline, do describe something real about where good teams try to play. The trouble starts when the idea becomes a variable and somebody has to decide precisely where the channel begins.

Different providers cut the pitch differently. Some use five equal vertical strips, some use the width of the penalty area to set the inner boundary, some define the zones relative to the position of the widest defender rather than the paint. Those produce materially different counts of the same match. A pass that registers as a half-space entry in one dataset is a wide entry in another, and neither is wrong, because there was never a standard to be wrong against.

If you have ever wondered why two analysts can cite opposite numbers about the same team's build up, this is usually why. Not bad faith. Different rulers.

The deeper issue is that the underlying idea is not really about a location at all. What makes the half-space valuable is body orientation and the defender's dilemma, whether the centre back steps out or the full back tucks in. A receiver standing in the zone with his back to goal and a defender tight to him has gained nothing. The zone is a proxy for a situation, and counting occupancy of the zone counts the proxy while ignoring the situation.

You can see the consequence in recruitment. Players get described as half-space specialists on the basis of touch maps, and touch maps show location, not what the location did to the defence. Some of those players are genuinely difficult to defend. Others simply stand there a lot.

What I would want counted instead is a defender's response: how often a receiver in that channel drew a centre back out of the line. That is observable in tracking data and it captures the actual mechanism, which is disorganisation of the defensive block rather than possession of a rectangle.

The zones were a teaching device. They were drawn on a whiteboard to explain a concept to players, and they were brilliant at that.

Turning a teaching device into a measurement instrument, without ever agreeing where it starts, is how a good idea becomes a bad statistic.