Prior to the disaster on Sunday, Arsenal were showing great signs. Unbeaten in the previous five games in all competitions and winning 4. We had plenty of reason to be optimistic going into the North London derby. However, this is Arsenal and the story in recent years is if you get your hopes up, you will be let down and most likely, it will be due to a blatant error from someone in defence.

Mikel Arteta has improved Arsenal defensively, there's no doubt about this. We have a better balance about us and as a result, we've been able to defend better as a unit, reflected by 3 clean sheets in our last 5 Premier league games.

Jose Mourinho, speaking post yesterday's game said: "To be honest, I think Mikel Arteta has found a way for them to play and to be stable and to improve. They are improving."

This 'stability' has led to improved individual performances from some defenders. A better structure has led to fewer frequency in blatant errors over time, but it hasn't all disappeared. No matter what system you give them, our defenders have managed to find new ways of throwing games away - I can safely say that a mistake is going to be made in the next 3 games because that’s how we’ve been for some time now.

In football, everytime a goal is conceded, you can view it as a defensive mistake. But I'm not speaking about minor positional errors at all. The fact of the matter is that the mistakes we made this season on many occasions are simply unforgivable at this level.

Under Unai Emery, the games were end to end. The distances were all wrong and there was a huge gap between midfield and defense. There was bad defending in every other game, but I felt sympathy for our defenders at the time because not many in world football can look solid in such a setup.

Under Arteta, we’ve seen an improved structure, but have continued seeing these errors, even if it is at a lower rate. Against Crystal Palace(A), we switched off during a set piece, Luiz dreaming away and that lapse in concentration led to the equalizer. Then at Stamford bridge in that famous 2-2 draw, Mustafi makes a really poor header into no man’s land which Tammy Abraham was able to chase and win a penalty with Luiz being sent off in the same play. If there was a defensive sequence to sum us up, it is this. 

Conceding from a set piece or from a second ball after the set piece has become a theme, with our central defenders just not being alert enough to deal with a situation. As project restart resumed, we saw Luiz at it once again, an absolute shambles of a display against Manchester City. 

The following game against Brighton, the defence once again goes to sleep in 2 moments which proves to be the difference. Mustafi and Rob Holding (who is usually calm) didn’t cover themselves in glory losing key duels at an important stage. Once again, in the first goal, a second ball off a set piece proves to be our undoing. It goes beyond zonal marking, or man to man marking or any other tactical setup – it comes down to how alert you can be and read situations quickly. And we just arean't. 

The North London derby back pass by Kolasinac was frustrating, but if you were someone who watched Arsenal throughout this season, it wasn't something surprising. To add on to this, Kolasinac had looked shaky in that position for quite a few games and far from composed on the ball which makes him a liability for us at center back - a ticking time bomb waiting to explode just like most other players in the defence. And explode it did…

Arteta has taken this defence as far as he can, what we saw in the last 5/6 games was our defenders  at their very best. We still don't look too convincing. As harsh as it sounds, Gary Neville's 'uncoachable' tag holds some weight. 

Arsenal have struggled defensively in a back 4 for ages. Arteta is trying to adapt to our defenders by changing the system and they still continue letting the team down. The 3-4-3 is a good temporary fix, but I don't expect it to continue into next season. What I see transpiring is a 4-3-3. A player like Thomas Partey can help us control the ball better. The more you can retain the ball and control games, the lesser you have to defend. 

It is imperative to invest in a marquee centre back and pair him alongside William Saliba. I am completely okay with Saliba making mistakes as he’s 19 and will only learn. We have so called experienced centre backs who never really learn, do they? It is a game of fine margins and the errors have often proved to be the difference between a draw/loss and a victory. Arteta said that we fix these errors and we win more games. As cliche as this sounds, his point is correct. Saliba's return, Chambers coming back and an improvement in this area through recruitment will prove to make a big difference in the long run.