Marcelo Diaz and Charles Aranguiz partnership at the heart of Chile's Copa America hopes

There is no side at this Copa America so tactically flexible as Chile, capable of switching from a back four to a back three in the blink of an eye, and that – along with a relatively simple group and a phalanx of in-form forwards – is the reason they’ve scored more than twice as many goals as anybody else in the competition so far.

They began the tournament against Ecuador with a formal back three, but quickly ditched that, relying instead on a loose 4-2-3-1 shape, but with Marcelo Díaz dropping in between the two central defenders, Gary Medel and Gonzalo Jara, to play at times almost as a third central defender, releasing the two full-backs, Mauricio Isla on the right in particular, to attack.

That is what gives Chile such a thrilling variety of angles of attack, how at times they seem to be coming from both sides and through the middle simultaneously.

Díaz and his partner at the back of the midfield, the more attacking Charles Aránguiz, are the unsung heroes of this Chile side. They’re the players who give balance, who offer at least some sort of platform for the rapid interchanges of the rest.

Díaz, who joined Hamburg from Basel in January, is the defensive key. 2.7 tackles and 1.7 interceptions per game are decent if not overly eye-catching figures for a ball winner – although they may be expected to rise as Chile face better sides as the tournament progresses – but what is key is that he combines that with a 91.7% pass accuracy. He wins the ball back and he holds onto it.

That may suggest somebody who is only a distributor, looking always to play the simple short ball, but he averages 4 long balls per game; only three midfielders or forwards – Javier Mascherano, Willian and Nestor Ortigoza – have played more, and of them only Mascherano has a better pass completion rate.

That capacity to play the ball forward directly is vital to the verticality Chile’s style of play demands. Their game is all about pressing high, winning the ball back quickly, and rapid transitions from back to front. Díaz’s importance in that, as defensive screen and launcher of counter-attacks, is huge.

But he perhaps would not be as effective as he is without Aránguiz alongside him. Aránguiz’s runs from deep have been a key feature of this Chile and they mean that even when sides have dealt with the first attacking wave, they have to be aware that a second may be on its way.

Aránguiz is another of the many Chileans who seems to play far better for his country than his clubs. He was part of Jorge Sampaoli’s Copa Sudamericana-winning side at Universidad de Chile before moving to Internacional in Brazil last year. Since joining Colo-Colo in 2009, his record shows he tends to score every five or six games, and he has six in 36 for his country. He specialises in goals against Bolivia – his two on Friday took his tally against them to four, but he also delivered the coup de grace against Spain in the World Cup.

But goals are only part of it. Like Díaz, Aránguiz is a ball-winner and a passer: 2.3 tackles and 0.7 interceptions per game, along with a pass completion rate of 88.8%. Again, a high pass completion rate shouldn’t be taken as an indication of an unadventurous passer: he is averaging three key passes per game in this tournament – more than any other player - and has one assist.

The pair work superbly in tandem. Both win the ball, both distribute sensibly, one sits and protects and the other, if the situation allows, makes forward surges. There are still questions about Chile’s defensive capacity in wide areas, but if they do go on to win their first ever Copa America, it will have been as much about the midfield base as the sparkling attack.