A full back occupies the wide defensive positions of a back four. The term originally comes
from the 2-3-5, where the full backs were the two deepest positions defensively, closest
to the goalkeeper – they were fully back, as opposed to the half backs, who occupied
the next line.
As the systems in football evolved and the back four was formed as a defensive unit,
these outside players retained their name, and their numbers; in England these are traditionally
2 and 3, but these numbering systems vary across world football, especially for the
right back.
In a traditional 4-4-2, width came from the wide midfielders or wingers, and so the onus
on full backs was largely to provide defensive cover against the opposition wingers and play
the ball forwards to them in the wide areas or, more directly towards the space in front
of them for a striker to peel wide and pick up.
However, in the last few decades full backs have become increasingly important in an attacking
sense, largely because formations became narrower further up the pitch. In a 4-3-3 or a diamond
midfielder shape, there is limited natural width – this means that there is no player
who ‘naturally’ finds themselves towards the touchline for crossing or being a receiving
option out wide. Full backs took on this role – good examples are Cafu and Roberto Carlos
in Brazil’s 2002 World Cup side, or Liverpool’s Andy Robertson and Trent Alexander-Arnold.
Inverted full backs also push up to assist with build-up but unlike the more traditional
attacking full back, they do not do so into the wide areas, but rather come inside towards
the middle of the pitch. They make a second line in front of the centre-backs, usually
flanking a defensive midfielder. This is where ‘inverted’ comes from, not simply the
idea of playing a right-footed player at left back or vice versa.
Pep Guardiola is usually credited with this innovation while at Bayern Munich, where he
used Philippe Lahm and David Alaba as inverted full backs. It’s also worth noting Marcelo
Bielsa’s use of Arturo Vidal for Chile at the 2010 World Cup where he pushed up and
in during build-up alongside the two defensive midfielders to make a three-man line.
The reasons for doing this is a possession-based team are fourfold:
Firstly, by inverting the full backs and pushing them up and in to create a second line (which
allows a team to resemble a 2-3-2-3 or the old 2-3-5), the central midfielders are covered
and able to push higher, playing as 8/10s who can play in between the lines and precipitate
attacking moves and provoke opposition uncertainty, but crucially while being covered.
Secondly, this cover also allows a team compactness in the centre of the pitch which means that
should the ball be lost there, with two full backs and a defensive midfielder in place
the team can press effectively. This means this line doesn’t only offer cover, it creates
a numerical superiority which aids winning back the ball.
This numerical superiority also helps in build-up, the third reason. Before the central midfielders
push high, it’s likely that the team will have significantly more players in the middle
areas of the pitch, the part that Guardiola always looks to dominate, and therefore many
more passing options.
And lastly, it can open up the wide areas. If the opposition wide midfielders or wingers
tuck inside and follow the full backs to mark them, they cannot double up to assist their
own full backs. It also can allow the team to shift the ball quickly to the opposite
side where a channel is very open for attacking.
Like any system, there needs to be flexibility. Inverted full backs need to be able to assess
the game conditions and adapt, otherwise the centre can be clogged up against teams who
sit back in a low block, and the lack of an overlapping runner can force the team’s
midfielders to run wide instead, leaving the centre too open higher up the pitch.
But that is why this sort of system is used by teams, like Bayern or Manchester City,
who have access to intelligent and flexible footballers who can make those decisions.
Used well, inverted full-backs can facilitate extreme attacking pressure while also shoring
up the defensive structure, allowing teams like Guardiola’s Bayern and Manchester City
sides to dominate possession and pin teams in their own half to devastating effect.