Arsenal's campaign this season has been geared around maintaining their top four status above all else; anything less will be regarded as failure and conclusive proof that the club have not only stalled under manager Arsene Wenger, but regressed, so in order to achieve their aims, do they require strengthening at the heart of their defence this month?

To say that the much-vaunted 'Steve Bould effect' has worn off would be something of an understatement. For those of us that found their early season form at the back explainable due to the nature of their opposition rather than anything diametrically different about their organisation, the effect was never there in the first place.

That is not to say that Bould is at fault by any stretch, just that these problems are systemic and deep-rooted in the personnel and culture of the club and it always helps more if you're cooking with the right ingredients. Bringing in a new coach and attributing any improvement to him simply because he used to be a defender too is a rather simplistic way of approaching matters and if the club's form this season has taught us anything, it's that there is no quick fix.

Since the start of November, Arsenal have participated in 20 games across all competitions and kept just five clean sheets (Aston Villa, West Brom, Wigan, Montpellier and Swansea in the FA Cup third round replay). During that three-month sequence they've conceded 28 goals and at the time of writing, they sit four points adrift of rivals Tottenham in fourth place. Despite keeping just seven clean sheets in the league this season, they still boast the fourth-best goals against tally of 27, but it's the little and often sloppy goals that are proving difficult to weed out.

Any hope that Wenger may be tempted to invest in a few fresh faces this month was quickly put to bed at the 63-year-old's press conference earlier today where he told reporters: "I don't worry - what I worry about is getting the injured players back fit and getting the players at this club to perform to full potential.

"We don't expect any miracle from outside, we want to make things happen from inside. If someone else can strengthen our squad we will of course do it, but we have the resources inside to do well.

"We have two players in every position and that should basically be enough, but if we find top-class players in any position we never refuse to strengthen our squad."

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With Sebastien Squillaci almost certain to move on at some point this window back to a club in France and Johan Djourou being loaned out to Hannover, the statement that they have 'two players for every position' is a disingenuous one. Firstly, because it implies that these players are of sufficient quality and time and time again their failings have been cruelly exposed in any game of importance this past year. They patently are not all good enough, with the side picking up just one point out of a possible 15 on offer against this season's top three.

Secondly, because in captain Thomas Vermaelen, Laurent Koscielny and Per Mertesacker, they have just three centre-backs to last them the rest of the season, which is not mathematically correct when you factor in Squillaci leaving and it leaves the squad short in an area where they are already weak during the most important time in the season. When the inevitable injuries arrive, as they always do at Arsenal, Wenger is not leaving himself much leeway in terms of numbers and personnel at the back, even factoring in the fixture schedule becoming a tad more forgiving at approximately one game per week as opposed to the hectic festive period we have just come out the other end of.

Of course, Wenger has never been a man to divulge his transfer intentions at a press conference, so we should still be somewhat guarded that his words were deliberately misleading, more out of hope than anything else, but he must surely realise the need to strengthen at the back, even if it's just in private, is not only important but necessary.

The time for 'potential' has long since come and gone with regards to 27-year-old Laurent Koscielny, perhaps the most talented of the three mentioned above. He is capable of fantastic last-ditch blocks, superb positional play and sound awareness at times, but is far too inconsistent, and the side have conceded 17 goals in the 13 league games the Frenchman has started this term, with his recent red card against Manchester City after switching off and allowing the fairly cumbersome Edin Dzeko to glide past him unnoticed, merely the best example of that lack of concentration which has afflicted his game this season.

The form of skipper Vermaelen hasn't helped matters much either, and instead of the imperious, authoritative presence many have come to expect, we get a nervy mess lacking any sort of positional discipline, wandering out to the left too far (probably due to his spell covering there last season for injury, he's never been the same since) and leaving gaping holes through the middle to exploit. According to Opta, while Koscielny has been directly responsible for three goals this term, the Belgian tops that with five.

The only centre-back to emerge with any credit so far has been Mertesacker, who has comfortably been the club's best defender this season, at fault for just one goal all campaign. He can get dragged to the ball at times and his lack of pace is still a notable flaw, but he simply makes less mistakes than the others and by the low bar which we are judging Arsenal's central defenders these days, he has done reasonably well.

We should also take into account the form of those around them too, though, as opposed to just blaming them outright and without context. The midfield lacks a ball-winner, with Alex Song's summer departure hitting them harder than initially realised, with Jack Wilshere trying to perform the job of two men at times and the gamble made on Abou Diaby being able to contribute anything more than a handful of appearances fully fit hasn't paid off. Mikel Arteta can perform a shielding job well, but he does not provide the energy and combativeness that is sorely missing at times.

At left-back, Kieran Gibbs has been understated but consistent and he is having a productive year, but the form of Bacary Sagna and Wojciech Szczesny is also a cause for concern. Sagna looks as if he would rather be anywhere else than Arsenal right now, with his shocking performance against Chelsea testament to that, while the Pole in goal looks dreadfully short of confidence. This all adds up to a back five unit which really doesn't know whether it's coming or going, even if injury and suspension have inevitably played their part.

Wenger can clearly spot a centre-back (Toure, Campbell, Vermaelen before the slump) but he's seemingly so reluctant to spend money to help address an area of weakness that it borders on the baffling. This current incarnation of Arsenal always seem to pose a threat at the other end, even if they are profligate in front of goal at times, and the spine is in reasonably decent shape, but if the club wants to secure Champions League football for a 17th successive season, a new centre-back above all else wouldn't go amiss, with a holding midfielder also right at the top of the list of priorities.

To simply put off investing in the side as a point of principle is akin to watching the last train leave while you're sat still on the platform. To stand idly by and let a top four place slip out of the club's grasp is unforgivable and Wenger needs to swallow his pride, put the best interests of the club first rather than his reputation and spend to ensure they don't miss out, otherwise you sense they may be counting the cost for years to come as the gap between the top two and those just below them increases by the season.

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