Arsenal: Arsene Wenger Needs to Buy Another Left-Back This Summer

Manchester United manager Sir Alex Ferguson is renowned for his adherence to the principle that success in football begins at the back.

It starts with finding a reliable keeper. Once that's taken care of, one can move onto the back four. There must be steel in those positions, and there must also be consistency.

It's easy to diagnose some of the reasons for United's success these past six or so seasons. They won the 2006, 2007, 2008 and 2010 Premier League titles using largely the same framework in their "back five," as it were.

With Edwin van der Sar as keeper, and Nemanja Vidic and Rio Ferdinand as the go-to defensive spine, the Red Devils could make do with John O'Shea and the Da Silva twins at right-back, and Patrice Evra (who has often been named team captain) at the left.

It was in the consistency that one could find the secret to their success.

It would be fair to say that while Arsene Wenger may have attempted to adhere to that script in recent seasons (although it is difficult to see the Frenchman ever taking pointers from his Scottish rival), he has certainly not enjoyed the same levels of success.

Wenger spent rather large sums (for him, anyway) to bring in center-backs Thomas Vermaelen in 2009 (an initial €10 million fee, which rose to €12 million), Laurent Koscielny (£10 million) and Sebastien Squillaci in 2010 (£6.5 million), and then binging on three defenders this past summer.

The arrivals of central defender Per Mertesacker (£8 million), Andre Santos (£6.2 million) at left-back and Carl Jenkinson at the right (£1 million) during the 2011 transfer window were not splashy signings, but they were serviceable options.

And as has been shown this season, Arsenal are still in desperate need of dependable cover at the defensive positions.

It must be noted as well, for all the critics who've said Wenger has failed to adequately address the defensive problems that appeared to be at the root of so many of the Gunners' collapses in recent years, the French manager did, in fact, spend fairly large sums in a concerted effort to address the problem.

Six defenders brought in over the course of 25 months is nothing to scoff at.

And yet, it still doesn't seem enough.

Squillaci has been an unabridged failure, Mertesacker is out for the rest of the season, and Jenkinson is still some years away from being a consistent contributor.

Johan Djourou is certainly never going to inspire much hope as the next-choice option at center-back behind Koscielny and Vermaelen, though the Swiss stopper got another chance to prove his mettle against Wolves on Wednesday while Koscielny serves his two-match league ban for picking up his 10th yellow card of the season.

Looking at the long term, Koscielny and Vermaelen have given every indication that they are a pairing that will work. Whether or not Wenger adds on another defender this summer as cover is up to him.

Moving to the situations at the side-backs, Sagna is another player who looks certain to continue to be the first choice on the right. The Frenchman has been excellent this season. With Jenkinson as a serviceable backup to him, that looks set for the moment.

We move, then, to left-back where, in my opinion, Wenger has to take a long look this summer.

At first glance, the situation would appear to be covered with Kieran Gibbs and Santos as the two foremost competitors for the position. But Gibbs has never shown he can stay healthy for more than a couple months, and Santos has never exactly inspired confidence in his ability as a defender.

Both are talented when able to get forward, but can either be relied upon for an entire season? Up to this point, the answer must be "no." Gibbs' groin pull, suffered against Manchester City this past Saturday, cast an immediate pall on that answer.

Santos is excellent when he is able to get forward in attack, but he has never looked a sure thing in defense.

Stuart Robson, commentating Arsenal's match against City over the weekend, put it well when he said that "Santos is a great footballer, but he is not a great defender."

Against Wolves on Wednesday, a game Santos started at left-back in place of the injured Gibbs, the Brazilian was once more exposed on the flanks.

Wolverhampton are far from a prodigious attacking force, scoring just nine goals in their last 11 matches—a spell that has seen them glean just one point from their last nine (including this most recent game against Arsenal). But there they were bombing in crosses on the right (Santos' side) with alarming frequency.

Wenger has yet to be seriously linked with any left-backs, although Jan Vertonghen, the Ajax defender who has seen his name associated with a summer move to the Emirates, can play the position.

With most of the transfer speculation being devoted to attacking options such as Lukas Podolski and midfield cover in the form of Yann M'Vila or Eden Hazard, Vertonghen's name certainly doesn't generate the same amounts of headlines.

But he may just be what the Gunners need most at this stage (and has expressed his desire to join the Gunners this summer).

With Jack Wilshere coming back next season, the midfield is already looking like it will again be Arsenal's strongest area on the pitch. "Check" that portion off the squad list.

Another striker would be a boon, but the left-back position should be addressed first. Build from the back.

Gibbs looks as if a full season is beyond him, and Santos is far from a sure thing. Thus, a strong spine—and one that will remain healthy—is an area that needs to be addressed soon.

Manchester City boast three options at left-back, with Gael Clichy, Pablo Zabaleta and Alexander Kolarov. Their current slide aside, they still remain above the Gunners in the league standings.

It's time for Arsenal get that kind of depth.