Manchester City still have the issue of Chelsea to deal with on Saturday when both sides meet in the FA Cup, but it’s not hard to imagine that Manuel Pellegrini and his squad have been keeping an eye on Barcelona these past few weeks, taking on whatever positives they can ahead of what is comfortably the glamour tie of this round of the Champions League.

The goals have dried up for Manchester City. It’s natural, after all, even in a team who have dispatched any manner of opposition with such ease this season. This dip in form also coincides with the loss of Sergio Aguero, who, despite the quality Edin Dzeko and Alvaro Negredo have shown this season, is far and away City’s most lethal forward.

The Argentine was otherworldly in the match at White Hart Lane before being taken off injured. Even though City only scored one of their five goals while Aguero was on the pitch, it was a performance that topped everything else they’ve done prior this season. Without him, and even with the other options available to Pellegrini, City don’t hit the same attacking heights.

The same couldn’t be said of Barcelona during the absence of Lionel Messi. The Argentine missed almost two months of this season, but in his stead, Neymar, Pedro and Alexis stepped up and helped to keep Barcelona at the top of the La Liga table. Now that he’s returned, Messi, you feel, has been gearing up for this crunch tie against City, contributing spectacularly this new year, but with still some way to go before it’s the fully fit Messi of old.

But it’s at the back where City will find some joy. Barcelona, of course, have an array of attacking talent who are more than capable of finding a way to goal against the best opposition in Europe. But they’ve shown themselves to be extremely suspect in defence in recent weeks.

The back-to-back losses against Ajax and Athletic Bilbao in November raised questions about the problems Barcelona have faced, though they’ve been largely to do with the attacking system employed under Gerardo Martino.

What has been crucial is that Barcelona no longer press high up the pitch and as often as they used to under Pep Guardiola. They still do so, but in bursts, rather than with any regularity. It means weaknesses in the back line can be exposed, leaving defenders either outnumbered or in one-on-one situations which wouldn’t have presented themselves in the past. Moreover, Sergio Busquets being on form and in place to protect the back four is absolutely vital.

Over the past few weeks, both Valencia and Sevilla have given Barcelona stern tests, with the former picking up all three points at the Camp Nou and the latter coming extremely close to taking something from a game which saw Sevilla hit the post and Alexis score from an offside position.

On both occasions, Barcelona were pressed and harried themselves. Valencia in particular went in strong for 50-50 challenges, broke at pace towards the Barcelona goal and showed far more desire than the home side.

Sevilla, too, took the game to Barcelona, with Carlos Bacca heading against the post in an effort that once again exposed a clear and long-standing weakness for the Catalan side. In the loss against Valencia, Pablo Piatti, the smallest player on the pitch, headed in his side’s first.

Barcelona can be got at when the other side either match or surpass their intensity – yet it’s also a case of Barcelona themselves not turning up. Bilbao did it expertly in November, essentially beating Barcelona at their own game by limiting the time Martino’s side had on the ball. In that match, Barcelona only had two efforts on goal, both of which came in the first half.

Barcelona have shown a vulnerability this season, though that has been the account given from those who aren’t entirely happy with Martino’s style of play. Nevertheless, their attack remains particularly potent when their best players are on form, still able to beat anyone on their day. Due to Manchester City’s own defensive weaknesses, Pellegrini’s side are not the clear favourites they’ve been billed as leading up to this tie.

City can take some confidence from what they’ve seen from Barcelona at various points this season. But this tie isn’t a sure thing. Both sides have clear defensive weaknesses, yet considering the importance of the occasion, you’d have to imagine both will be at their best.

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