I was thinking on Sunday how come it is possible for Chelsea to have won most or all duels in the midfield,I forgot about these two great players that made up a huge chunk of Manchester City success and I fully believe in that saying in football,your midfield either wins you games or lose you games,showing the importance of this department of the team,for me being the most important in the team,just look at all the glorious teams through the years not only here in Premier League but also other leagues and you will see super performing teams had always the best midfield.
I get what you mean when you say that the midfield is the most important part. I think it depends on the team's style. But the saying, if I recall that correctly, usually goes like this:
“Attack wins you games, defence wins you titles.”
and I believe it is from Alex Ferguson. I think that statement makes a lot of sense. There are some clubs that have been extremely successful because they had the strongest defense in the league. Atletico Madrid, Juventus Turin for some years and others as well.
But the midfield is the most important part for Manchester City because Guardiola trains his players so they can fill several positions at once and be more flexible than any other team. He likes to have have defensive midfielders, central midfielders and offensive midfielders and he likes defenders with midfielding qualities.

This means for Guardiola the midfield is definitely the most important part of his team. I think that is also why they are having some difficulties recently.