Asymmetric full backs are wonderful until you need to make a substitution

One side inverts, the other overlaps, and then your left back pulls up on the hour and the bench has nobody who does either job.

Building a team with two different full backs is one of the genuinely good ideas of the last decade. One tucks in and gives you a third midfielder in possession. The other stays high and wide and gives you a winger. The shape is lopsided on purpose, the opposition has to defend two problems instead of one repeated twice, and the whole thing looks clever in a preview graphic.

Then somebody gets injured on fifty-five minutes and the cleverness turns into a bill.

Squads are built on the assumption of like-for-like cover. Two left backs, two right backs, one of them a bit more attacking. That works when both flanks want the same thing. It falls apart when the left back's job is to play as a midfielder who happens to start wide, because the deputy is not a midfielder, he is a defender who is good at overlapping, and the moment he comes on your build-up loses a body in the middle and the far winger's isolation stops working.

Managers deal with this by improvising, and the improvisations are usually worse than they admit. Push a central midfielder out to the flank and you have a man who does the possession part and cannot defend a one against one for the last half hour. Flip the asymmetry to the other side mid-match and you have asked eight players to relearn their reference points with no training, which shows up first in the pressing, where hesitation is fatal.

The clubs that handle it best do something dull and expensive: they recruit the profile, not the position. The backup for an inverting left back is another player who can operate in midfield, whatever his listed position, and he is not cheap because everyone wants that player now.

There is also a cost people miss entirely, which is set pieces. Asymmetric shapes tend to come with asymmetric responsibilities on corners, and a substitution rearranges two or three assignments at once in a part of the game where confusion is how goals happen.

I would still build the team this way. I would just stop pretending the lopsided shape is free, and I would build the bench before I built the first eleven.