4 step explanation of how Arsenal's 3-4-3 formation under Unai Emery works

#2 High defence line

Emery does not allow more than 15-20 metres of space between the 3 lines of players

To accompany a press which is able to press till the goalkeeper, there always needs to be a high defence line to ensure that the opposition doesn't get a lot of space in midfield. Emery follows a simple philosophy of not having more than 15-20 metres of space between the three lines of players i.e the defence, the midfield, and the forwards.

While Sokratis sits a bit deeper, Mustafi and Holding are able to get more forward and play through balls as well as win headers before they even reach their own half.

Although this means that the defence is susceptible and wide open to attacks on the transition, it provides many advantages going forward. The ball-playing ability of Holding and Mustafi allows Arsenal to quickly switch play when the central midfield partnership of Torreira and Xhaka are unable to find space.

As seen against Tottenham, and to a certain extent Bournemouth, these switches have proven to be pivotal in starting attacks for two reasons - the sheer pace and ability to drive in via the wing backs Kolasinac & Bellerin, and the efficient overloads made in wide areas.