Neither side would have wanted this game to be sandwiched between two European Cup semi-finals – especially since both find themselves one goal down in their respective ties. Usually these sides have had a full week to prepare for the Clasico, or at least the opportunity to rest players ahead of it. This time, the most important game of La Liga season has suddenly arrived.

Barcelona: approach

Barcelona must win the match to have a realistic chance of winning the league. They trail Real Madrid by four points, and though Pep Guardiola will be hopeful his friend Marcelo Bielsa can do him a favour when Real Madrid travel to Athletic’s San Mames stadium, it’s highly unlikely they’ll drop points anywhere else. “If Madrid win or draw, La Liga is theirs,” says Guardiola. “For us it’s simple, we need to win to stay in the league a bit longer. If we don’t win, we’ll congratulate them because they’ll be champions.”

Real Madrid: approach

Real Madrid’s objective here is to avoid defeat. That makes their task simpler in theory, yet possibly more complicated. As Guardiola notes, Barcelona don’t have a choice about how to play. Real do, which means Jose Mourinho has an extra level of strategy to consider.

Barcelona: formation

Despite many experimentations with 3-4-3 and even 3-3-4 recently, it would be a surprise if Barcelona opted for a back three from the start. As Guardiola noted earlier in the season, it’s difficult for them to play that way unless they control the whole game, and they cannot be sure of controlling the whole game against Real.

But that could all change – in the reverse fixture, Barcelona basically shifted formation midway through, with Guardiola practically declaring afterwards that he wanted his side to start with a back four in order to trick Real, before switching to a three. Dani Alves and Sergio Busquets are the players that can function either at the back or in midfield at the same time (Busquets’ role in the previous league meeting was remarkable, playing centre-back and central midfield at once, a role which probably didn’t get the credit it deserved). But, at least on paper, Barca should start with a back four.

Real Madrid: formation

Mourinho’s default formation has been a 4-2-3-1, though he’s often changed that for the Clasicos in order to play a trivote, a three-man midfield. This has defensive connotations and would undeniably be a cautious move, but Mourinho will have watched Chelsea’s performance in midweek and seen how effective they were at denying space in central positions with three holders.

He will also have acknowledged that Real underperformed, especially defensively, in midweek when playing 4-2-3-1 at Bayern Munich. It was a surprise that Mourinho started Mesut Ozil as a number ten, rather than Esteban Granero, who would have played much deeper and allowed Real to compete against Bayern’s midfield three. The situation for this game is almost identical, and it’s difficult to see how or why Mourinho would want to persist with the 4-2-3-1 when the system he reverted to late on, with Granero in midfield, offers far more defensive protection in the centre.

Barcelona: selection

Barring any huge surprises, there are two and a half issues for Guardiola here. The first is the left side of Barcelona’s attacking unit. In midweek Andres Iniesta played wide-left. His ball retention skills featuring in the front three is a sign that Guardiola wants extra insurance that Barcelona will dominate possession heavily, at the expense of attacking thrust from a natural forward. If this was a cup match, or a game where Barcelona could afford to draw, Iniesta would probably be used as a forward again. But it is likely he’ll be brought back into the midfield, to make room for a true attacker like Pedro Rodriguez, who has endured a disappointing campaign, but does offer the type of runs Barcelona will need – in behind the defence from wide positions. This might mean Cesc Fabregas is dropped, after his poor finishing on Wednesday.

The second issue is at the back. Gerard Pique’s form has been dodgy this season, he’s still recovering from injury, and he missed the midweek game, where Javier Mascherano was preferred in the centre of defence. Pique may be recalled if Guardiola wants a defensively-solid player at left-back, as Carles Puyol could move out there. If not, and he wants more attacking drive, then Adriano will play at left-back and Pique is likely to be on the bench again. On form, Mascherano is no more of a gamble than Pique.

The half-issue is Alexis Sanchez, who would start if fully fit – but Guardiola says he’s doubtful for the game. Isaac Cuenca would stretch the play from the flank but doesn’t offer a significant goal threat himself, and if Sanchez doesn’t make it, Fabregas might get a reprieve.

Real Madrid: selection

Mourinho would have considered bringing Pepe into midfield, in the roving destroyer role he performed in the Clasicos last year – but he’s needed at the back for this match. Granero seems a logical choice alongside Xabi Alonso and Sami Khedira.

The other issue in the defensive part of the side is left-back. Fabio Coentrao was favoured over Marcelo in Munich, and neither covered themselves in glory – Coentrao with a mistake in the build-up to Mario Gomez’s winner, and Marcelo with a poor late tackle after coming on. But Mourinho might field both down the same flank, as he did towards the end of that Bayern game – either would be perfect for playing the Ramires role, tracking Alves and then breaking past him. Coentrao, who has played as a midfielder frequently this term, would probably be more suited to the higher position.

If Mourinho does play two left-backs – a strategy Valencia have used effectively against Barca – where would that leave Cristiano Ronaldo? Possibly on the right, which is the area Real will feel most ‘free’ in, but possibly as a lone forward. He doesn’t like playing there, as he sees little of the ball, but Mourinho’s only Real-era win over Barcelona came in the Copa Del Rey final when he did. He has both the pace to work the channels, and the height to cause problems in the air.

That would leave Angel Di Maria, Mesut Ozil and Karim Benzema fighting for the final position. Benzema would allow switching between him and Ronaldo, Ozil would be able to float inside as he did very well at the Nou Camp in the Copa del Rey earlier in the season (though that relied on Busquets being distracted by Kaka), while Di Maria is the natural option but is lacking fitness.

Depending on how Mourinho plays; two, three or even four of Ronaldo, Di Maria, Ozil and Benzema could start. But Ronaldo upfront and Di Maria on the right seems the most logical defensively, and that is the priority.

Barcelona: tactics

Barcelona’s approach on Wednesday was odd – they played with little natural width (hence why Pedro and Cuenca were introduced later on), yet also got outnumbered in the central zone where they wanted to play.

Here they need to stretch the play, expand the Nou Camp pitch and create an open game in the centre. If that means leaving 3 v 3 in the middle against a Real Madrid solely looking to break up play, so be it. Barca should have the faith they can win that battle.

The role of Messi is inevitably key. Barcelona are relying on him too much at the moment, and he needs more support in the penalty box. Part of the reason John Terry and Gary Cahill made so many blocks from Messi’s shots was because they weren’t distracted by other runners, which is usually a feature of Barcelona’s play. Again, this is why Pedro is important (and why Fabregas might be a better bet than Cuenca, even if he doesn’t offer the same pitch-stretching abilities).

But Messi’s role as chief goalscorer means he can’t drop too deep. Against Chelsea, and in that Copa Del Rey final last year, he got frustrated by the lack of service and dropped past the opposition holders, which gives Barcelona a 4 v 3. But in a way, it negates the point of him in that false nine role – which is that he stays between the lines and gives Sergio Ramos and Pepe doubt about whether they should follow or not. If he drops too deep, there’s no doubt, Real let him go.

Guardiola must be careful about the positioning of Alves, who was caught out in London. Real spent a lot of time in last year’s Clasicos hitting diagonals in behind the full-backs, and Alves must react intelligently according to who his direct opponent is.

Iniesta also has a big role in this game, as the link between midfield and attack. Barcelona’s passing at Stamford Bridge was surprisingly slow – Iniesta is the man who must provide the sudden change of tempo, and the incision. It’s also worth pointing out that Iniesta has the third-highest shots per game in the Barca squad (after Messi and the injured David Villa) but doesn’t contribute enough goals.

Real Madrid: tactics

Mourinho’s strategy against Barca so far this season has involved pressing heavily for the first few minutes, then gradually retreating into a deep position. That seems a favourable approach again, as Barcelona have been slow to settle down into their passing rhythm at the start of games.

The interesting player on the Real side is Khedira, who has the energy to close down in midfield. Mourinho could try to replicate what Chelsea did on Tuesday – sit deep, but use one man to close down higher up. Khedira’s mobility could be vital – even if it forces Barcelona to go sideways rather than play through the middle so readily, it will be useful.

But it will be equally fascinating to see how Real break. The space behind Alves is absolutely vital, and whoever plays on the left wing must be brave enough to realise when Alves has moved too high and wide and isn’t a huge attacking threat, leave him, and get into a position to break forward. Ramires did that perfectly. The role of the lone forward is also important – there’s no great point in him standing high up against the centre-backs, since they will be outnumbered and won’t be getting a great deal of support. Instead, they must work the channels, pull the centre-backs out of position, and possibly take up positions on the wing when the player on that side is back defending. Ronaldo seems best for this job.

Key questions:

1. Will Real press, and if so, for how long?

2. Where, and how frequently, is Messi receiving the ball?

3. Where are Barcelona seeking to create situations of numerical superiority, and which players are being dragged out of position in order to do this – can Real break past them?

4. How does the game develop – do Barca shift formation again?





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