Most teams inverting their full backs are copying a solution to someone else's problem

Stepping a full back into midfield fixes a specific weakness in specific squads, and everywhere else it is fancy dress.

The full back drifts inside, stands next to the holding midfielder, and the television graphic draws a little arrow. It has become the default signal that a coach is modern. It is also, in a lot of teams, straightforwardly harmful, and the reason is that the move solves a problem you have to actually have.

The problem it solves is this. You dominate the ball, you play against low blocks, your central midfield gets outnumbered when you commit players forward, and you keep losing possession in areas where the counter hurts. An extra body in the centre during build-up gives you a spare passer, a better shape for the counterpress, and a way to keep the opponent's wide forward from breaking against your exposed flank. All of that is real, and if you are a side with seventy per cent of the ball and a full back who is a natural midfielder, do it.

Now consider a team that has forty per cent of the ball, whose most dangerous route to goal is a fast winger in space, and whose full back is a full back because he is quick, defensively sound and reliable in a one against one. Invert him and you have taken your best defensive width away, put a man who is uncomfortable in traffic into the most congested area of the pitch, and given your winger nobody to combine with. The graphic still looks contemporary.

There is a squad building cost that gets ignored too. The inverted role needs a specific player, comfortable receiving under pressure with limited space and time, capable of turning away from contact, a genuine passer. Those players are scarce and they cost money. Buying a normal quick full back and telling him to play in central midfield is not a tactical innovation, it is asking a good player to do the thing he is worst at, sixty times a season.

Tactics travel badly, and they travel worst when they are copied from the very top, because the very top has resources and problems nobody else has. A treble-winning shape is a description of one squad's particular imbalances, not a template.

I would rather watch a team do something unfashionable that suits its players.

The arrow on the graphic is not the point of the game.