Lots of debate on here about whether we need to be more defensive once leading and whether we will need better defenders in the future, countered by opinions that we are scoring more by being more aggressive.
However, the 2 need not be in conflict. We play a high pressing game - which means that our midfield 5 are often well up the field pursuing the game. This is Tufty's style. If you press high it is absolutely crucial that your back line also presses up so that the space between midfield and the back line is small. If your back line sits back, then when the opposition come through or over the midfield they have a big space in which to run at you, and you are in trouble.
I have noticed that when we are pursuing the game early on our back line does press up, but particularly once we are ahead they tend to sit deeper - this is a psychological thing as you feel that you are playing safer. Unfortunately, for the reason above, it is counterintuitive and much less safe. So, you either need a disciplined back line - and a strong intelligent leader to run it and keep that gap small - or, as others have suggested, you can include a strong DM like Kante to patrol that space.
I haven't looked back at different games, but maybe one thing Jake Wright does is to drive the back line closer to the midfield.
As an aside, I thought that Lafferty was very weak on their disallowed goal, put no pressure on that first header.
At the other end, Lavery, Carruthers and O'Shea are as lively as a bag of ferrets, and must be a nightmare to defend against.
UTB