AC Milan are one of the world's most decorated sides but they are still considered underdogs at home. Barcelona will be missing some players, most notably David Villa, while Mario Balotelli is cup-tied for Milan. What can we expect from the Rossoneri?
The trophy cabinet at AC Milan is stacked. The Italian club has won 18 international titles, joint-most in the world with Boca Juniors of Argentina. They have been world champions four times, more than any other club. Why is a team of that magnitude so unfancied?
Well, it has to do with the cost-cutting measures of Silvio Berlusconi, the notorious politician and the team's president, and the team's aging corps that needed to be replaced.
On the one hand, their two best players by some distance, Zlatan Ibrahimovic and Thiago Silva, were shipped off to Paris Saint-Germain to save money. On the other, the likes of Alessandro Nesta, Filippo Inzaghi, Gianluca Zambrotta, Gennaro Gattuso, Mark van Bommel, and Clarence Seedorf, decorated veterans all, have left on free transfers or retired.
In their place, a core of talented but young and unpolished players have struggled to reach the heights the club is used to. Teenager Stephan El Shaarawy has been phenomenal and leads the team in scoring, but Milan got off to a slow start as the squad gelled.
At the quarter point of the season, Milan were 12th. By the halfway stage, they were seventh. Now, they sit fourth, invigorated by the midseason arrival of Mario Ballotelli from Manchester City. Crucially, however, Balotelli is cup-tied in European competitions and thus is unavailable against Barcelona.
Clearly, this is a team in very good form. They have only lost one out of their previous 13 league matches, and that run included a 1-0 win over the champions, Juventus.
Milan boss Max Allegri has made slight variations to his formation, as he has employed a 4-3-3, a 4-2-3-1, and a 4-3-2-1 at different times, but they are broadly similar.
Allegri frustrated Pep Guardiola's side last season, with an extremely narrow formation at the San Siro. That, combined with an extremely dry pitch, neutralized the slick Catalan passing attack and the match ended in a 0-0 draw.
The Milan boss cannot rely on booting long balls to Ibrahimovic anymore as he did in that game, but it's likely the Rossoneri will again try to sit back narrowly and hit Barca on the break. El Shaarawy is not small, but he's not all that tall either. Instead he may need to chase a few long passes.
Allegri could bet on defensive midfielders to break up the Barca attack, or he could attempt to play fast wing players in sacrificial roles like Sir Alex Ferguson did against Real Madrid. Manchester United started with Wayne Rooney and Danny Welbeck on the flanks mainly as defensive workhorses.
El Shaarawy may only be nineteen, but Il Faraone has clearly been Milan's best player over the course of the season. The top-scorer for the side, he is also second in the Serie A scoring charts behind Napoli's Edinson Cavani.
"SAS", as he is sometimes known, was rested in the league match against Parma as he was experiencing some discomfort in his knee. The Rossoneri faithful are optimistic that he will be fully fit to face Barca.
Balotelli has been very good since his arrival, and he's already third on the team in scoring ahead of Bojan Krkic. However, his contribution will be in moral support for this game, as he is unable to play in the Champions League having already played for City.
Milan made an enormous error letting playmaker Andrea Pirlo join Juventus on a free transfer two seasons ago. Pirlo was the Turin side's best player as they topped Serie A last year. This year, they've made amends, at least somewhat, with the acquisition of Riccardo Montolivo.
The Italian international is not of Pirlo's level, but he's been a consistent force in the midfield. He has recovered possession and played more passes than anyone in the team, and can deliver consistent long balls as well.
A few youngsters have caught the eyes of the fans. One is M'baye Niang, who recently arrived from French side Caen. Niang is exceptionally physically gifted: a six-foot-two player who can still run. Niang has been compared to Balotelli both for his on-the-field talent and his off-the-field issues.
Mattia De Sciglio may not be a household name yet, but he's quietly established himself as a key player at right-back. De Sciglio is a Milan youth team product, capped at youth levels for Italy. Really on his first season as a first-team regular, De Sciglio has good tackling technique and can cross the ball playing on either flank. He is also an option at center-back.
Christian Abbiati should start in goal, and though he's not been consistently great this season, he has been good playing against Barcelona lately.
Luca Antonini remains a fringe player, but he is an option on the left as well. Daniele Bonera is useful in any position along the backline, but he is coming back from an injury and unlikely to be fully fit.
Montolivo will be needed to help in ball recovery and distribution, which will leave two other spots open in midfield. Antonio Nocerino should take one of those spots in midfield, as he's troubled Barca in the past, including scoring a goal at the Camp Nou the last time the two sides met.
The last place on the teamsheet is a bit more difficult to predict. The poly-functional Kevin-Prince Boateng has been good, though not necessarily at his best, this season. (He, too, scored a goal against Barcelona in the past Champions League campaign.)
Massimo Ambrosini or Mathieu Flamini are midfield players who would provide more naturally defensive options than Boateng. Meanwhile, Nigel De Jong is out on a long-term injury. Could Sulley Muntari, back in action after a knee injury, be part of the team?
The forward line, missing Balotelli, will be difficult to predict. Of course, SAS should start if healthy, and in all likelihood he will. The other spots could go to two of Bojan, Giampaolo Pazzini, or Niang.
Of the three, Pazzini is the most proven while Niang is the most raw. Pazzini, who was acquired in exchange for Antonio Cassano before this season began, is recovering fitness after an injury. Niang is seen as a great prospect but is years from achieving it.
Bojan is well-known at the Camp Nou and could be back next season, but he's yet to unleash his full potential and some question whether his development has already flatlined.
Robinho, who knows all about great promise never fulfilled, is not projected to be fit enough to take part in the match. Boateng is also an option up front. The talented but oft-injured Alexandre Pato has left the club in the past transfer window.
The more attacking approach is to name Boateng in midfield and play three forwards, likely El Shaarawy, Pazzini, and Niang, or possibly Bojan. The more cautious approach would be to play the likes of Flamini or Ambrosini in the middle and Boateng in an advanced midfield role, or perhaps as a wide forward.
AC Milan are a young team, rediscovering its identity in a trio of exciting forwards with ludicrous hair. Balotelli, El Shaarawy, and Niang are seen as the cornerstones of the post-Ibra, post-Nesta, post-Silva, post-Seedorf Milan.
However, Niang is still young, Balotelli is cup-tied, and El Shaarawy is coming back from injury. Their moment is not now, at least, it shouldn't be.
But the team is solid in general - a bit suspect defensively, sure - but full of good players. At home, Milan will hope one of its good strikers, of which they have many, will score against Barca's troubled defense.
Perhaps the world is underestimating the Italian side just a bit? We will see.
Possible XI: Abbiati; De Sciglio, Mexes, Zapata, Abate; Montolivo, Nocerino, Ambrosini; Boateng, El Shaarawy, Pazzini (4-3-3)