Some things, it seems, never change. If this were a soap opera – and the Premier League can often feel like one – you’d say that the characters of Arsenal and Tottenham Hotspur have stagnated. They’re both in desperate need of some new storylines, rather than the eternal issues of Arsenal having no defensive midfield and Tottenham suffering an inconsistency that means it habitually fails to live up to potential.

Saturday’s north London derby has the same backdrop it seems to have had for years. There was a time when, after a result like Arsenal’s 3-0 victory over Aston Villa last Saturday, it would have been said that the Gunners had answered their critics, particularly given Mesut Ozil and Danny Welbeck, whose performances in the 2-0 Champions League defeat to Borussia Dortmund had brought general dismay, both scored.

But people have gotten used to the pattern. Nobody seriously thinks beating a mid-table side – particularly one ravaged by an intestinal virus – proves anything for Arsenal. Of course it can do that. It’s capable of stuttering, particularly against robust or well-organized opposition, just as any side is, but essentially beating the lower two-thirds of the table is what Arsenal does.

What it has struggled with of late is not merely beating the top sides, but avoiding being absolutely hammered by them away from home. That’s why, by far, the most significant match for Arsenal this season was the game in Dortmund. Until then there’d been a gentle optimism. The signing of Alexis Sanchez maintained the excitement kindled by the five straight league wins and success in the FA Cup final at the end of last season.

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Frustration at a suggestion of toothlessness was assuaged by the signing of Welbeck. Even the bizarre lack of depth in terms of defensive resources – six players for four positions – seemed to be laughed off by many as just Arsene Wenger and his strange ways. Then came Dortmund. Arsenal was played off the park.

Dortmund was quicker, sharper, smarter and, on another day, might have scored five or six. Somehow a couple of misses from Welbeck that might have salvaged an implausible draw drew significant attention, but the issue was – as ever with Arsenal – at the other end of the pitch.

Mikel Arteta is many things, but a destructive midfielder he is not. He will make interceptions and he will distribute the ball well, but against a side like Dortmund he can be of use in only three ways: if he has a destroyer (or two destroyers) alongside him; if he is part of two compact banks of four denying the opposition space; or if he is part of a midfield five all working ferociously hard. Arsenal does none of those three things.

Jack Wilshere and Aaron Ramsey are both hard-working, will both shuttle up and down, are both good passers of the ball and both offer a goal threat (even if Wilshere’s has tended to be theoretical; that he, playing as he does, has managed just six league goals for the club is one of the great mysteries of the Emirates), but as a trio, along with Arteta, the three lack defensive coherence.

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There is, of course, Mathieu Flamini, who can tackle, but he has not looked in great form this season. The problem is exacerbated by the fact that if Ozil operates wide, he offers almost nothing in terms of defensive support, an issue that has repeatedly left his left back, whether that is Kieran Gibbs or Nacho Monreal, exposed.

Against teams Arsenal can dominate, it’s not an issue: it surges forward and has a great swarm of attacking midfielders interchanging position, creating intricate skeins of passing. Against better sides, Arsenal is inevitably left exposed. Ozil, in fact, creates a major headache. Play him on the left and Arsenal is left vulnerable to an attacking right back who can surge past him.

But play him through the center, where he apparently wants to play and where he played against Villa, and Wenger is forced to switch to a 4-3-2-1 and thus must choose between using Wilshere and Ramsey. Ramsey could, in theory, be deployed on the right, but that then means Santi Cazorla or Alexis Sanchez missing out.

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“We adapted the system slightly to play Ozil in the middle and he responded very well,” Wenger said after the win over Villa. “He prefers playing in the middle, but I can find you about 10 other players in my squad who would say the same.”

To which the obvious response is to ask why on earth he signed them all, rather than bringing in another couple of defenders or somebody who could dominate the back of midfield.

Arsenal will dominate weak sides and struggle against good ones; the problem with trying to work out what might happen on Saturday is that Tottenham could be either. If a comfortable home win, though, means little in the long run. Arsenal’s problem is obvious and long-standing: it is fatally focused on one end of the pitch.