A home crowd talks a defensive line into stepping up too soon

Noise is a tactical input, and the input it usually supplies is impatience at exactly the wrong moment.

The safest thing a leading team can do late in a game is drop five yards and defend the edge of its own box. The most popular thing is to push the line up and squeeze, because pushing up looks like courage and dropping looks like fear, and thirty thousand people have a strong opinion about which is which.

They express it audibly. A defensive line retreating gets groaned at. A line stepping out to catch a striker offside gets a cheer before anyone knows whether the flag is up.

I do not think this is a small effect. A back four holding a high line is running a continuous group decision under time pressure, and the cue to step is a shared read of the ball carrier's body shape. That read has to be unanimous within about a fifth of a second or somebody plays somebody onside. Add noise, add adrenaline, add a crowd that has been screaming for the team to get up the pitch for ten minutes, and the read gets biased towards stepping.

The centre-back who steps a fraction early is not being reckless. He is being social.

What makes it worse at home is that the compact block is precisely the shape a home crowd finds intolerable. Away from home the same defending is applauded, because expectations are lower and everybody understands the plan. That asymmetry is a real part of why home advantage does not do what it used to. Teams that would happily see out a one goal lead in a hostile away ground find they cannot do it in front of their own supporters, and they get pulled out of a shape that was working.

The counter is obvious. Professionals ought to be able to ignore this. Some can. The best defensive units seem to have one player who is loud, senior, and immune, and who simply keeps holding a hand up and shouting the line back down while everybody else is being carried forwards.

Squads without that voice concede in the ninetieth minute and nobody can explain why the line was so high.

The explanation was in the stands, and it had been getting louder for a quarter of an hour.