Defensive Weaknesses - this is the big one. The focus has been so strongly on the attack that it's almost been inconsequential that Barca don't keep too many clean sheets. But this is an issue - with Marquez and Puyol both proving to be very fallible. The Espanyol game was instructive - for the first goal, De La Pena ran into the far post, Yaya Toure tracked him but then stopped to watch the ball and Pena had a free header. For the second goal Valdez managed to kick the ball straight to De La Pena who made no mistake. Pique is inexperienced and Abidal is better going up than defending. The same can be said about Alves. And in tight European games when there's one goal or two that settles the tie, Barca cannot afford to be cavalier about their defence.

The Messi Situation: Everybody will point to a dependence on Messi but is this really such a big factor? We would argue that every successful team has a superstar that they tend to rely on. Be it Zidane at Madrid in the late 90s, or Gerrard at Liverpool, Ronaldo at Man United - the presence of such a magical player can never be considered a weakness especially when the players around him are all doing so well. Having said that, while Barca have steamrolled the opposition with the front 3, they've certainly looked less potent without Messi and Henry - so their presence over the rest of the season will be key to Barca's maintaining this form.

The Eto'o situation: this is more complicated. Eto'o seems to be playing well perversely, to prove a point to Barca, rather than as a real believer in the cause. His professionalism can't be faulted but rumours suggest he's angling for a move away and this could be an unwanted distraction at the end of the season.

The Midfield Situation: Iniesta's injury has created a bit of a problem for Barca and so far, Hleb's performances there haven't been all that assured. Xavi has not produced the form that made him player of the tournament in Euro 2008.Can Barca's midfield be out muscled? Busquets has been excellent and red-card apart Seydou Keita could be useful. But are they world-beaters?  

The Back Up Situation:A question that must hang around is - how good are Barca's second team? What if Messi wasn't available? Or Henry? Could Gudjonson, Bojan and and Hleb slot in smoothly? And is the first team being overused because of the lack of back up? Are Barca getting tired? And could they pay the price in key games? They have suddenly stopped winning - their last 3 games have been drawn or lost and they must hope this is a blip. But at this stage, the games come thick and fast and every game is important either for Barca or for their opponents. Will Barca have the stamina?

Madrid factor: They've been here before and lost it from here. Madrid have in recent history made a good fist of hauling back a big lead. This will play on the Catalan minds. Already, you hear Arsenal-like utterances from Barca about anti-football and complaints about teams being physical or ultra-defensive against them. But the psychological battle in the days to come will be a big factor and Barca will have to be strong in the mind as well as the body to stay top over the next 4 months.

The Guardiola situation: Pep Guardiola has had a fantastic first season and it must give Barcelona no end of joy to think about the number of years of service he could give them, if things keep going well. But right now his inexperience is a factor and how he tackles every new challenge is going to be key. Each of these situations is new - the first blip in form, the first difficult Champions League game... and Guardiola will be under the microscope. He could come through with flying colours, but it's certainly going to be a factor.

Seven points is still a big margin and lets not forget, people are talking about handing the title to United with the same margin. But it's for Barcelona to throw away and this could get more interesting yet.

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