Video review made stepping up a worse bet

The offside line used to be judged by a human eye that gave defenders a margin, and defences quietly priced that margin into their shape.

Before frame-by-frame review, a defender who stepped up and got it fractionally wrong often survived. The assistant was watching two things at once from an imperfect angle, the benefit of doubt tended to go somewhere reasonable, and a shoulder ahead of the line was invisible. Defences knew this. The offside trap was a bet with a built-in cushion, and the cushion was worth playing for.

Take the cushion away and the same tactic becomes a different proposition entirely. Now a defender who steps a fraction late is not offside by a shoulder in the eyes of an official standing forty metres away, he is onside by a toe on a still frame, and the goal stands. The risk did not change. The forgiveness did.

You can see the response in how sides defend now. Fewer teams play an aggressive line as a primary weapon and more use it situationally, on set restarts and when the ball carrier's head is down. That is a rational adjustment. What surprises me is how rarely it gets described as a tactical consequence of technology rather than a fashion, because it is one of the clearest examples in the sport of a rule being enforced differently and behaviour changing in response.

There is a second effect that runs the other way and is less discussed. Attackers used to hold a deliberate half-metre of safety, staying visibly onside because they did not trust the assistant. That caution is gone too. Forwards now time runs to the millimetre and accept marginal calls, because a review will confirm what a human eye could not. So the line got riskier for defenders and more precise for attackers at the same time, which is a double shift in the same direction.

The tolerance debates miss what is actually being argued about. A margin of a few centimetres is not there to be accurate. It is there to restore some of the forgiveness the old system provided by accident, because the sport was balanced around that forgiveness for a century without ever noticing.

Precision was the goal. Nobody checked whether the game had been designed for it.