If you push the line up, your goalkeeper is a defender now

Playing a high line with a shot stopper who lives on his goal line is not brave football, it is an unforced error.

Thirty yards of open grass behind the last defender has to belong to somebody. Either the centre backs defend it by dropping, which means you are not playing a high line at all, or the goalkeeper defends it by starting outside his box and reading the through ball before it is played. There is no third option, and yet plenty of teams pick one.

The goalkeeper who can do this is doing something quite unlike goalkeeping. He is judging the passer's body shape from forty yards, deciding within about half a second whether to come, and then covering ground in a straight line towards a striker who is also sprinting, with the additional detail that he may not use his hands once he leaves the area. Get it right and you have effectively added a defender. Get it wrong and you have conceded, been sent off, or both, in front of everybody.

That risk profile is why the position splits opinion so violently. Errors by a sweeper keeper are spectacular and legible. Errors by a passive keeper are invisible, because a striker running through unopposed onto a bouncing ball just looks like good attacking play. The cost is identical. Only one of them ends up in a compilation.

I would take the argument further than most. If a manager wants a high line and his goalkeeper cannot or will not leave his box, the manager should abandon the high line rather than hope. Systems fail at their weakest joint, and this is the joint. Building a team around aggressive compression and then hoping nobody plays the obvious ball over the top is not a plan, it is a wish.

There is a skills development point buried here that annoys me. Goalkeeper coaching still spends most of its hours on shot stopping, which is the part of the job that has been shrinking in relative importance for twenty years. Distribution got added because everyone could see it on television. Space defending, the reading and the sprinting and the decision to stay, remains under-coached because it is harder to drill and much harder to assess.

Watch how far off his line a keeper starts when his team has the ball in the opponent's half. Twenty yards is a system working. Six yards is a system with a hole in it.

The best defensive signing some clubs could make is a keeper who is comfortable being wrong at the halfway line.