There was a time when you could build a defensive identity around the offside trap. Not just use it — build around it. Arsenal's back four under George Graham stepped up like a drill team and made a genuine competitive advantage out of it for the better part of a decade. Sacchi's Milan did something similar with more sophistication. It was a weapon and everyone knew it.

It's basically gone now. Teams still play high lines, obviously, and there are still offsides. But the deliberate, choreographed trap — the one where the whole line steps at a signal specifically to catch a runner — has quietly disappeared from the top level, and I don't think it's coming back.

Reason one: the margins got smaller

The obvious one. When offside decisions were made by an assistant referee's eye at 30 metres, the trap was a percentage play. You stepped, and if you got it roughly right, you'd get the call more often than not. Doubt tended to favour the defence in practice, whatever the letter of the law said.

Now the margin is measured. A toe. A shoulder. The technology draws a line and the line doesn't care about your intentions. Which means a trap that used to be right 80% of the time is now right maybe 60% of the time, and the 40% is a striker running through on goal with your entire defence facing the wrong way.

That's a terrible risk profile. The upside of a successful trap is a free kick to you in your own half. The downside is a clear chance against. You need to win it a lot to break even, and the technology took away exactly the marginal calls that made the maths work.

Reason two: the runs changed

Here's the more interesting reason, and it's a coaching story rather than a technology one.

The offside trap works against runners who commit early. If a striker sets off from a standing start and accelerates into the space behind, he's beatable — he's moving in one direction and can't stop. The trap catches him.

Modern forwards mostly don't run like that. They run curved, they run late, and crucially they start from a position level with or behind the last defender rather than trying to beat him. Watch a well-coached forward attack the depth now: he's checking towards the ball, dragging the line up, and then bending his run outside-to-inside so he's arriving at the moment the pass is played rather than waiting for it.

Against that, stepping up doesn't catch anybody. It just gives him more space to run into. You're moving away from your own goal while he's moving towards it, which is precisely the geometry you're trying to avoid.

Reason three: goalkeepers can pass now

This one is indirect but I think it matters. A high line is only viable if the space behind is defended, and increasingly that space is defended by the goalkeeper rather than by an offside call.

The sweeper-keeper isn't new — Neuer didn't invent it, and Rogério Ceni and others were doing versions of it long before. What's new is that it's standard. Almost every top-level keeper now starts 15 to 20 yards off his line when his team is in possession in the opposition half. That's a completely different defensive proposition to a keeper on his six-yard box.

And once you have that, you don't need the trap. You can hold a high line, accept that some balls will go over it, and rely on your keeper to get there. It's a more robust solution because it doesn't depend on eleven players getting a timing decision right simultaneously.

What defenders do instead

The modern equivalent of the trap is a lot less dramatic and a lot more effective: line integrity plus pressure on the passer.

The principle is that the defensive line's job isn't to catch anyone offside, it's to stay flat and stay connected to the midfield, and the job of preventing the ball in behind belongs to whoever is nearest the man with the ball. If the passer is under pressure and can't lift his head, the run behind is irrelevant because the pass isn't coming.

This is why you'll hear coaches obsessing about the distance between the last defender and the deepest midfielder rather than about the line's forward movement. Compactness is the modern version of the trap. Squeeze the space vertically, force the ball wide or backwards, and the through ball never gets attempted.

Where it survives

Two places, roughly.

Set pieces, oddly. You still see teams step out together after a cleared corner, and it works, because the attacking players are stationary and reacting rather than running with intent. It's the one situation where the old geometry still applies.

And lower down the pyramid, where the technology doesn't exist and the assistant's flag is still a matter of judgement. I've watched non-league defences win a genuine advantage from an aggressive trap in recent years, and it's a slightly nostalgic thing to see. Whether it's good coaching or just exploiting the officiating I'll leave to somebody else.

I do miss it a bit, honestly. There was something wonderful about a back four rising in perfect unison, arms up, a whole stadium turning to look at the linesman. It was defending as performance. But it was also a high-variance play that only made sense in a world with fuzzy edges, and we don't live in that world anymore. The edges are sharp now, and sharp edges reward the boring, reliable version of everything.