What a modern full-back's job actually consists of

A position defined by its surroundings

The full-back occupies the corridor between the touchline and the centre, and what the role demands depends almost entirely on how the rest of the structure is arranged. Where a winger holds width, the full-back is expected to provide underlapping runs and support in the half-space rather than overlapping outside. Where the winger comes inside, the same player must supply the entire width of the attack and cover the ground to do it repeatedly.

In systems using an inverted arrangement, the full-back moves into midfield in possession and performs a role bearing no resemblance to the traditional one. Because these arrangements differ so much, two players with the same nominal position may be doing almost nothing in common.

Conflicting duties in the same phase

The defining difficulty of the role is that its attacking and defensive responsibilities frequently apply during the same passage of play. A full-back supporting an attack is simultaneously the player responsible for the space behind them if possession is lost in a wide area. Managing that tension means constantly judging how far to commit, which is a decision made under time pressure with incomplete information about the rest of the field.

Teams reduce the burden structurally, by having a midfielder cover the vacated space or by asking one side to advance while the other holds. Where no such support exists, the individual carries the whole trade-off, and any error is highly visible while the correct restraint is invisible.

Defending in isolation

Full-backs defend one against one more often than any other position, because wide areas are where isolation can most easily be engineered by an attacking side. The defensive requirement is therefore specific, involving controlled retreat, delaying without diving in, and shepherding an opponent towards support or towards the line. Body orientation matters enormously, since the defender must show an attacker in one direction while remaining able to react if they go the other way.

Recovery ability is part of the same requirement, because a beaten full-back is the last line on that side and the situation escalates immediately. None of these qualities appear clearly in the counting measures typically used to describe defensive contribution.

The delivery question

Attacking output from the position is usually judged by crossing, which is only one of several ways a full-back can contribute in the final third. A player asked to deliver from deep is performing a different task from one asked to reach the byline, and the two require different techniques entirely. In systems that avoid crossing, the same player may be judged on their ability to combine in tight spaces and to retain the ball under pressure.

Because the mandate varies so widely, comparing delivery figures between full-backs in different systems compares instructions rather than ability. Establishing the mandate first is therefore the entire foundation of any honest profile of the position.

Why output profiling misleads here

The measurable output of a full-back is largely determined by the structure they play within, which makes raw figures a poor guide to capability. A player in an attacking system accumulates final-third involvement that would be unavailable in a conservative one, regardless of their own qualities. Conversely, a player in a defensive structure accumulates defensive actions because they face more of them, not because they defend better.

Profiling the role therefore means describing what is being asked and then judging execution against that specific brief rather than against a general standard. Done carefully, it produces a far more stable assessment than any comparison of totals between players in different systems.