I actually really like this formation. Chelsea play it very well, as do watford on the occasions when they aren't getting dicked 6-1. Thing is we have the best wingbacks in the league by a mile so it suits our players and gives us more cover defensively for out of position players. We've essentially been playing this way since last season though when dier was splitting toby and jan at DM. It isn't that different to our usual 4-2-3-1/4-1-4-1
It's definately different from 4-2-3-1, because of some very important adjustments. I will try to explain why, and why it is not a defensive 5-x-y formation.
In a 4-2-3-1 you absolutely need a holding midfielder to avoid being to exposed when you full/wing backs support the attack. When on the attack, it is crucial to cover space to prevent counter attacks.
If you let both your side backs join the attack, and you don't have a DM, you are only left with two CBs with too much space to cover. If you have a DM sitting deep, you can allow you two CBs to cover a little bit wider, to cover some of the space left behind the side backs. However, with the DM sitting in front of the CBs, the two CBs can not allow too much space in between them. That means that you can mostly only allow one of the side backs to join the attack, or else you might get too exposed on the sides. That means you have to have four men with primarily defensive duties when you attack. Also, as the wide forwards in a 4-2-3-1 tends to be played in a manner where they are to drift inwards, meaning you will lack some width on the side of the full back having to stay back. Some teams deal with that issue by playing a true winger in front of a more defensive side back.
In a 3-4-3, the third CB sits between the RCB and the LCB. As the third CB is more on line with the other two, the RCB and LCB can go a little wider, thus offering better cover in space left behind the wide men. That allows the wide men to attack more freely, meaning e.g. that Walker can be in the box on the receiving end of a Rose cross, something we practically never see in our 4-2-3-1. It means we have more width to our attack, that we have a player coming in from the side to attack the far post on a cross from the other side - a player it's more difficult to pick up for the opposition defenders.
Even in a 3-4-3 you might want a midfielder with somewhat more of a defensive responsibility, but not as defensive as in the 4-2-3-1, meaning fewer players are primarily defensive in the 3-4-3.
The issue in 3-4-3 is that there might be space for the opponents to exploit particularly centrally between our defence and midfield, and if that is exploited that it will most likely create space on the sides when our CBs deal with the threat. However, for a team that manages to run a lot, to be aggressive and on the front foot, the system is superior particularly as it allows more players involved in the attack, but also as it is very defensively solid when we are under heavy pressure, as it THEN can be turned into a 5-4-1.
:walker:
