I see some people were reading over my shoulder yesterday when I was writing a post that was trashed when my browser crashed.
Maybe I can shorten what I tried to say.
It seems to me that the defence, as such, isn't great, but it's not as bad as our "goals against" suggests. In my opinion the problem is that they're under constant pressure because the midfield don't break up opposition moves enough.
Sawyers, as much as I like him, isn't capable of doing that. He's better further up the pitch but he can't play DM. Livermore is out for at least 3 games.
Gallagher is nailed on to be one of those in central midfield, whether there are two or three there. So who takes the other spot(s)? Gallagher isn't a defensive player, or if he is we'd lose his power going forward and I think that would be counterproductive, but we do need at least one player to do that job. Probably two.
I think we only have Field and maybe Ajayi (who I think has played that role at previous clubs), but you lose the latter out of defence if you do that, which means your CHs are going to be 2 or 3 of Bartley, Ivan, O'Shea, and maybe Kipre. I think the only other possibility as DM is Peltier