The problem with Arsenal’s defence is one of two things: either they are just not playing very well at the moment, or as a unit they’re simply not very good any more. In other words, it’s a loss of form or a loss of class.

I’ve had an interesting Twitter exchange for the last couple of days with Times journalist Daniel Finkelstein on the subject of the Arsenal defence. Mr Fink published some stats about Arsenal on Saturday that claimed we did not need to worry too much, as we still have the sixth best defence in the Premier League. Well you might say that based on last season’s statistics, I said, but look at our current form.

“I’m not a believer in form,” said Mr F. “Class is all. You are slipping but still sixth at the mo.”

“But,” I pointed out, “form wins matches! Class might keep Arsenal from relegation, but not if form doesn’t change, therefore form is more vital.”

Oh no it isn’t, he replied. Form is essentially random. His exact words were, “Form is an illusion caused by randomness. If – if – you have class you will win clusters as well as lose them.”

Well this is true up to a point, in that we know that every team will have runs of good and bad results during a season and we can’t predict in advance when those will occur. Last season Chelsea started with six straight wins while Man Utd were slower out of the blocks, but that didn’t last forever. Most people knew Chelsea wouldn’t win every game in the season, and equally Man Utd would start to win more. We just didn’t know when it would happen.

But Arsenal at the moment – well, that doesn’t look entirely random to me. So I tweeted back: “Form has elements of randomness, but [in Arsenal’s case is] also caused by transfer window madness & no defensive coaching! Time alone won’t cure [it].”

Ha! I’ve got him there I thought. But he was soon back with this: “That wouldn’t be form, that would be semi-permanent decline in class and in defence that has been happening.”

Hmm. Well he’s moving the goalposts there, isn’t he. On the one hand he reckons it’s safe to say that on the basis of last season we have the sixth best defence in the league, and on the other he’s saying, actually, in Arsenal’s circumstances – assuming I’m right – perhaps we’re getting worse.

Well perhaps that sixth ranking needs to be changed then, I pointed out.

And he conceded that maybe it would be soon, but a decline in class is usually slow. In other words, don’t worry too much because even if the Arsenal defence is worse than it used to be, it would be unusual for it to be a lot worse very quickly, and thus the current habit of conceding goals approximately every five minutes is a temporary blip that our old friend randomness will sort out soon enough.

I can see his point. Against Blackburn we had two own goals, an offside goal (marginally), a penalty not given and about 5,000 missed chances. All that won’t happen every game (apart from the 5,000 missed chances), and on another day we could have won. Maybe not convincingly, but we could have won. Overall you could easily argue that the performance was as good or better than the Swansea game.

So I’m in agreement that results will get better and this bad run will come to an end. The question is really are we getting worse, particularly in defence?

We used to have a fantastic defence. We used to concede about as many goals in a season as we have so far in this one. Arsene got lucky, very lucky, with what he inherited, because as the years have gone on it has become clear that he doesn’t really know so much about defence. So is the defence worse than it was from 1997 to 2002? Yes, definitely. Sol’s arrival kept the decline in check for a while as the likes of Adams, Keown, Bould, Dixon and Winterburn gradually departed, and Cashley was more than capable as a player if not a man.

The last six or seven years have seen definite decline from those glory days, but how far? There are two ways to look at it.

One – Even if things look appalling now, remember that Mertesacker and Santos are still new, and Vermalaen is missing, so maybe it will all work out. We are in a temporary defensive blunder-ridden blip.

Two – Wenger’s defensive knowledge could be written on a stamp and his tactics on a tic tac, so decline is inevitable. Wrong players, wrong ideas, wrong system. In the words of Private Frasier, we’re doomed.

My opinion? Wenger knows sod all about defence and ignores the basic need to counter opposition tactics and defend set pieces. It’ll be a long season.