Manuel Pellegrini
Manuel Pellegrini faces some important selection dilemmas as Manchester City head into their clash with Barcelona. Reuters

As Barcelona have largely reigned over the European landscape in recent years, their quivering opponents have almost exclusively adopted the strategy of hanging on for grim life against the wave of incessant passing, hoping to have just a chance to test what has always felt like a susceptible defense. That is not a way that their opponents in the Champions League Round of 16 know or you suspect have any intention of playing. It is what makes Barcelona’s two-legged duel with Manchester City a potentially riveting slugfest.

It is a battle between two sides who like to play the match on their own terms. One is a great power under suspicion of being on the wane, the other an upstart with desires to burst the lucrative ceiling into Europe’s elite.

There are plenty of subplots off the pitch, but on it there is more than enough to whet the appetite. For the first time in more than five years, since Pep Guardiola’s glorious evolution of the club’s playing principles yielded an unprecedented stockpiling of trophies, there is a the sense of a genuine uncertainty and vulnerability about Barcelona. A 7-0 defeat to Bayern Munich in last season’s semifinals still looms large.

It was not a result the came out of the blue -- Milan and Paris Saint-Germain had both given them plenty of problems in the previous rounds -- yet it was stark to see Barcelona’s flaws laid so bare. To many, those issues still remain. There can’t be many clubs who could face such harsh scrutiny in a season in which they have led the league for all-but one week, progressed through the Champions League group phase at a canter and will play in their domestic cup final.

Barca’s Attacking Diversification
The club’s third coach in as many seasons, Gerardo “Tata” Martino, has faced an unenviable task of dealing with the philosophical and political battles at the Catalan club while trying to produce a winning team on the pitch.

One of his first challenges was to abate what had become a detrimental dependence on Lionel Messi. The club addressed the issue, in theory, with the expensive capture of Neymar.

The Brazilian has generally settled well at the Camp Nou and showed just the type of individualistic game-changing ability he was sought for with a wonderful run and long-range thunderbolt against Rayo Vallecano at the weekend. Yet, after a month on the sidelines with an ankle injury, there is a good chance he won’t start at the Etihad on Tuesday.

Still, Barcelona’s move away from an over-reliance on Messi extends beyond Neymar. Both Alexis Sanchez and Pedro, who look likely to start alongside Messi, already have more goals to their name this campaign than throughout the whole of last season. The two have been given the encouragement and responsibility to flourish, both when Messi spent two months on the sidelines and since the Argentine has returned. Martino has made a subtle shift of getting Messi to drop deeper and take on more of a creative role, as shown by his seven assists in his last six appearances.

An unfamiliar problem has instead emerged for Messi, that of struggling to find the net. After a concerning spell for their talisman and a more worrying one for the team, encouragingly, Barcelona come into the match with City on the back of one of their best performances of the season in which Messi scored twice in a 6-0 demolition of Rayo Vallecano.

Problems still remain, of course. Xavi, now aged 34, is not as influential as he once was and with his declining physical attributes can now be bullied out of games easier, as he was so devastatingly against Bayern. Indeed, there is a strong argument that Cesc Fabregas should play in Xavi’s stead; the former Arsenal man having been arguably the club’s best player in recent weeks.

Issues Remain In Both Defenses
It is Barcelona’s unresolved issues at the back, though, which will most encourage City that they can truly announce themselves on the European stage. On paper their defensive record looks strong, but they hide the true story. Against most opponents, possession is almost all the defense that is required to come out on top. But even with little sight of the ball, teams are posing Barcelona real problems. Even Rayo forced Victor Valdes, another unsung reason for Barcelona’s strong defensive record, into some sharp saves despite being thoroughly outplayed. The imposing center-back that Barcelona have been calling out for since Carles Puyol’s physical decline has still not arrived, with much faith being put on the promising but still raw Marc Bartra. The vulnerability at the back remains as prevalent as ever, particularly from set-pieces.

That defensive susceptibility is something Barcelona share with their opponents at the Etihad. Manchester City, too, have failed to address their need for a center-back to complement the superb, but too-often injured, Vincent Kompany and extremely promising, but still developing, Matija Nastasic. With Nastasic injured, Kompany’s partner against Barcelona is likely to be Martin Demichelis. Barcelona’s players will know the Argentine well from his time at Malaga. They, if not relishing his presence, will certainly not be in the least bit daunted by it.

Like Barcelona, though, City have been boosted by their weekend performance. Against Chelsea on Saturday, when City produced a much-improved display to avenge their loss against the same opponents two weeks earlier, Manuel Pellegrini’s side denied their opponents the opportunity to counter and harried their danger men especially.

Still, Barcelona are a very different proposition. While Chelsea were exposed for their lack of true playmakers, Barcelona have them in abundance. And should City be caught pushing men forward, Barcelona now also have an increased capacity to sit back and make hay with fast-paced counters. Indeed, that subtle shift and the willingness to hit long diagonal passes was one of the subtle changes that earned Martino much criticism from the Barcelona purists early in his reign.

Pellegrini’s Tactical Dilemma
Should Pellegrini be overly adventurous, that evolution could pay rich dividends for Barcelona. The Chilean, who knows all about Barcelona’s threats having faced them with Villarreal, Real Madrid and Malaga over a nine year spell, faces some crucial selection dilemmas. With Sergio Aguero still out, as he will be on Tuesday, Pellegrini opted against playing two out-and-out strikers against Chelsea. Instead he modified his approach with the inclusion of Stevan Jovetic as a more versatile forward, able to drop deep into midfield and drift to the left to cover David Silva’s roaming inside.

The returning Samir Nasri replaced Joveitc on Sunday to offer more solidity. It may be that Pellegrini starts in that shape against Barcelona, with the aim of preventing Barcelona from getting a stranglehold in midfield as Bayern Munich were able to do earlier in the season under former Barcelona coach Pep Guardiola.

With Fernandinho having a chance of recovering from injury to take part, City’s midfield options look strong. The balance is further evident by the pace and width on the right of Jesus Navas, who could be key in getting behind the forward-thinking Jordi Alba. Up front Alvaro Negredo has a blend of physicality and quality to single-handedly cause Barcelona’s defense problems.

On home soil, if City get the balanced right they could well leave with a first-leg advantage. Yet, there should be enough goals at both ends to keep viewers riveted and the tie still very much alive heading to the Camp Nou.

Prediction: Manchester City 3-2 Barcelona