By 1970's Gooner
I have long been advocating that Arteta and Flamini should be starting games for Arsenal. They provide a more efficient shield of the back four (especially when Konscienly and Debucee are absent) than when one of them along with a more forward thinking midfielder are fielded.
This is because the 'other' midfielder is more attacking minded and /or not disciplined enough to stick to his position. The result is an unbalanced formation which lends itself vulnerable to counter attacks.
Wenger says that we played a 4 4 2 formation against Burnley. Well it was more of a 4 4 1 1 formation.
This formation, apart from playing two solid defensive midfielders, allows Wenger to bring Sanchez away from the flank and alongside or around Welbeck.
Sanchez does not stick to a particular position for too long and his desire to track back and fight for the ball enables him to be an extra player in midfield. This is especially important when we don't have the ball and the opponents are due to start an attack or worse start a counter attack.
Overall this is a more balanced formation than before which allows for a more solid defensive cover but at the same time does not curtail the offensive nature of the team.