Well, of the many reasons, the most obvious is that the shape helps create
numerical advantages in defensive situations which makes teams more defensively sound.
It isn’t coincidental that some of the supposedly weaker sides in Euro 2020
have opted for a three-man defensive system, with Finland,
North Macedonia and Hungary all examples of teams who have utilised a 3-5-2 during the tournament.
This particular formation allows them to force opposition buildup play wide,
as two strikers block vertical passes, three midfielders congest the centre of the pitch
behind them, and the wing-backs then gain a two v. one advantage against an attacking winger.
If the opposition is able to get the ball into the box from a cross,
the advantage of playing three central defenders vs two is obvious - there is
one more body to contest aerial balls, therefore making the defence stronger.
Weaker teams tend to select a 3-5-2 or 3-4-3 because they expect to have
less of the ball than their opponents and need to protect against that disparity.
Additionally, the most likely way they can expect to create chances is on the counter-attack, so by
sitting back and blocking space, then attacking with wing-backs and a couple of forwards,
they maximise their defensive output and exploit an opponent in a vulnerable attacking shape.
Some managers will fit players into a 3-5-2 or 3-4-3 system because it’s how they want to play,
while others select it because it suits the personnel available.
Scotland are an example of this as it helps them get left-back Andy Robertson
in the same starting XI as fellow left-back Keiran Tierney.
It’s not just lower ranked teams who utilise a three-man defensive shape though. Belgium have
spent a long time as the number one-rated team in the world and have some of the best
players on the planet to choose from. So why does Roberto Martinez prefer a 3-4-3?
One reason might be that in order to play the sort of possession-based,
high press, attacking game he wants to, it is essential to ensure there is defensive balance,
or at least a safety net to guard against the counter-attack.
Playing a 3-4-3 means that not only do they benefit from the same advantages as weaker
sides - ie being far harder to break down and score against when out of possession - but because
they are so good in attacking situations, they can enjoy the best of both worlds.
Belgium have central defenders comfortable on the ball who can play passes out from the back,
or carry it into midfield to help create overloads. The wing-backs can
get higher up the pitch from a higher starting position than full-backs,
requiring less defensive cover from midfielders, which helps gain control of opposition territory.
One negative is that playing an extra centre-back means losing a more creative player higher up the
pitch but in tentative, cagey international games, the more defensively solid teams have something of
an advantage - look at Greece in 2004 or Portugal in 2016 for winning examples. It only takes one
goal to win a game after all, and for some teams that is precisely what they’re looking for.
A back three doesn’t necessarily mean a team is defensive. Johan Cruyff’s incredible Netherlands
team of 1974 nearly perfected Total Football using one, and Pep Guardiola’s Manchester City
regularly transition from a back-four to a three in an increasingly common shape seen used by Italy
at Euro 2020, as one full-back tucks in and another advances.
Some managers use 3-5-2 and 3-4-3 formations to help in buildup,
most use them because they help weaker sides defend in greater
numbers to frustrate superior opponents. It is far easier to destroy than create,
and for some teams, their best chance of winning is by blocking and stopping the opposition,
hoping the few opportunities they then get to counter will lead to winning attacks on goal.