The situation regarding Arsenal's back four has created a rather unusual paradox. While the club's defenders have come under scrutiny for some poor showings - a particularly woeful performance against Liverpool comes to mind - they have conceded just once more than league leaders Manchester United, and their record is the fourth best in the Premier League.

Yet, there has certainly been something lacking at the back for the Gunners this season. In the big games at least, the likes of Thomas Vermaelen, Bacary Sagna, and Per Mertesacker have been found wanting, with the Arsenal captain held accountable by the Sky Sports punditry team for both of Tottenham's goals in the North London Derby, in which the Arsenal back line was stretched and penetrated by some flowing attacking moves on the part of Tottenham Hotspur.

But as my old Sunday League coach used to remind me as a young boy on a regular basis - defence starts with the attack. The phrase has two simple meanings; firstly, the best way to defend is by having the ball and attacking the opposition goal, and secondly, a whole team is accountable for defensive duties, not simply the back-line.

With that in mind, perhaps the focus on Arsenal's defensive frailties should not be aimed at the defence itself. Theo Walcott for example, although being an exceptional threat going forward, provides little cover for his full back, and is quite simply not built for or mentally programmed to be a useful element in his side's own third of the pitch, and I would argue a similar analysis regarding Lukas Podolski.

But the concept of using wingers has always had an element of risk involved. In the modern English game they are expected to track runs and provide cover for those behind them, but it is still accepted that they must focus on attacking. In the 4-5-1 formation that Arsene Wenger deploys, more freedom is given to the wide men, which is expected to be balanced out by the additional body in the middle of the park.

However, that is arguably where the problem lies for the Gunners. Their first choice midfield three, composed of Jack Wilshere, Santi Cazorla and Mikel Arteta is full of flair, creativity, technique and skill, but there is a distinct lack of metal to provide some balance to their attack-minded personnel in the middle of the park.

Arteta is usually Arsenal's most deep-lying midfielder, and although his contribution to his side's passing game is a valuable asset, with a pass completion ratio of 92.4% - no easy feat when averaging 80 passes per game - he is certainly not what you'd describe as a natural defensive midfielder, ball winning midfielder or screening midfielder. In fact, during his Everton days he was on the most part fielded on the wing.

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Venturing through the club's roster, there is certainly a lack of this type of player. The only two members of the squad who Wenger has to naturally fill the role are Emmanuel Frimpong and Francis Coquelin. Although both are promising youngsters, they are still a long way away from becoming first team regulars at the Emirates, and the former has spent the season farmed out to Championship clubs in order to gain some experience and recover from his serious injury last year while on loan at Wolves.

When required to use the squad's depth, Wenger has relied upon Aaron Ramsey to step in. But the Welshman is arguably even less defensively capable than Arteta, and is not headstrong enough to take the responsibility of breaking up attacking moves, especially fast-paced counter-attacks when the opposition are directly running at him. Numerous times this season I've witnessed the 22-year-old back off and fail to close down quick enough, despite it surely being his first priority when being used as a holding midfielder.

The Arsenal teams of the past have always been attacking minded and based around free-flowing football and ball retention, but at the same time they included a physical element in the middle of the park that anchored attacks and provided considerable defensive contribution. The obvious example is Patrick Viera, who fulfilled a holding role whilst "The Invincibles" played around him safe in the knowledge the Frenchman could clogg up any gaps left behind while going forward. Similarly, Gilberto Silva was brought in to overtake the role and in recent years the position has been claimed by Alex Song, whom departed for Barcelona in the summer.

And it is the Cameroonian's presence which has been missing this season especially. There's a rather large Song-shaped hole in the Arsenal side, which has left the back four too easily exposed and has furthermore hindered their capability of defending set pieces - a recurring problem for the Gunners this campaign.

It is not that Mikel Arteta doesn't do a decent job - he tackles, he intercepts and he moves the ball on comfortably, progressively and precisely. But it is not the job Arsenal require. The Spaniard lacks that monolithic athleticism in terms of strength, pace or defensive awareness that other physical midfielders in the Premier League possess, such as Yaya Toure, Marouane Fellaini and Sandro for example.

So perhaps Arsenal's defensive failings this season can be traced back to a simple transfer faux pas. Whilst Alex Song made a summer departure, Arsene Wenger quite simply did not replace him. Instead, the transfer kitty provided by the defensive midfielder's £15million move to Nou Kamp, along with Robin van Persie's £20million exit to Old Trafford, was spent on bringing in Santi Cazorla, Olivier Giroud and Lukas Podolski.

Of course, 'What If' is a rather pointless question, but you get the feeling that if the Gunners had a defensive element in their midfield, some of their lacklustre results may have been avoided - a particular smash and grab display from Swansea early in the season, which got the fans' backs up, comes to mind. Although I believe Wilshere, Cazorla and Arteta on paper is as good a midfield trio as any other in the Premier League, its lack of balance has cost Arsenal dear in terms of results and points on numerous occasions this season, especially against the top teams, which has been the club's biggest failing.

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