Barcelona's Woeful Defending Continues in Clasico Loss to Real Madrid

January 10 was the last time Barcelona kept a clean sheet.

Cordoba were the visitors to Camp Nou for a Copa del Rey match and Barca won 5-0, a few days earlier they had beaten Espanyol 4-0.

Much has been made about La Blaugrana's decreased potency in the attacking phase of their game, but Karim Benzema's sixth minute opener in Saturday's El Clasico made it 13 consecutive games in which Barca have conceded.

The last time this run of conceding in consecutive games happened?

Between January and March, back in 1962.

The last two games of this run will have hurt the most, though. Real Madrid following up the Copa del Rey win with a 2-1 La Liga victory at the Santiago Bernabeu.

So while they may be lacking the edge going forward, which has led them to so much silverware in recent seasons, they also have gaps at the back which desperately need plugging.

It is, of course, fairly safe to assume that against most sides Barcelona will simply score more than their opposition. But the upcoming make-or-break Champions League tie with AC Milan may not prove as simple as that.

The Italians will bring a 2-0 lead to Spain from the first leg, and if they score, Barcelona will need to score four to progress.

But why are Barcelona having so many problems keeping goals out?

A common suggestion seems to be the inclusion of two attacking full backs. In the past the galavanting, attacking nature of Dani Alves's game was balanced out by a more solid, defensively sound left-back—Eric Abidal for example.

Now, with Jordi Alba offering a similar attacking outlet to the Brazilian on the left, it seems that Barca's centre-halves are being left more exposed.

This excellent piece from  Last Gasp Goal takes a look at the problems the two attacking full backs may be creating defensively.

Another problem is that Carles Puyol—as demonstrated by Angel Di Maria on Tuesday night—is not quite the phenomenon he has been. He is 34 now, but despite that, his Barcelona career does not seem to be coming to an end particularly soon. He recently signed a new deal, but his contributions in big games is beginning to decrease.

On the other side of the coin to partner Gerard Pique, is Javier Mascherano. It's no secret that the Argentinian was signed from Liverpool as a defensive midfielder, but Barca have since turned him solely into a central defender.

He's shown on numerous occasions how well he can play there, but like Puyol, his contribution in the big games—as expected for someone who's played most of his career as a midfielder—is often questionable.

You could even go as far as to wonder whether Victor Valdes' decision not to renew his contract, and the uncertainty over who will be Barca's No.1, is having some sort of effect.

There are no simple solutions to stop leaking goals.

Maybe Jordi Roura can ask Alba to play a more discipline role, it's more likely he could do it than Alves.

And as for Puyol and Mascherano, neither are bad defenders—far from it. But with it imperative that Barca don't conceded against Milan one of them—most likely the former—will have to display their concentration and defensive ability for the whole 90 minutes.

If not then Barcelona could be facing a lonely end to the season, despite the fact the La Liga title is nearly won.

What do you think are the solutions to Barcelona's defensive dilemmas? How can they keep AC Milan out?