Arsenal's formation

Towards the tail-end of last season, Arsene Wenger opted to use a 3-4-3 formation and it worked well for him as the Gunners went on to beat Chelsea and lift the FA Cup.
This season, Wenger chose to stick with the system that worked for him but in just two Premier League games, Arsenal have already conceded 4 goals.
If Wenger opts to use the same system against Liverpool, then it could be suicidal.
Hoffenheim used the same formation against Liverpool and Sadio Mane exploited the space between the wingbacks and the central defenders very well. For Arsenal, this could be a huge issue if Chamberlain plays as the wingback because Mane or Salah will have very little trouble bringing to fore his defensive vulnerability.
The other issue is that Wenger has persisted with Monreal in a three man defence and his inexperience playing as a centre-back could make things easier for Liverpool. Not every Spanish full-back is Cesar Azpilicueta.
In such a formation, Arsenal will also be outnumbered in midfield as they will have two central midfielders against Liverpool’s three. Even for a team like Hoffenheim which uses a more intense pressing game than Arsenal, they had no answer to the pressing and closing down of Liverpool’s midfield three.