AC Milan's Sulley Muntari (R) scores against Barcelona during their Champions League soccer match at the San Siro stadium in Milan February 20, 2013.[Photo/Agencies]

Even Barcelona top scorer Lionel Messi, who has netted in the last 14 La Liga matches, struggled to make his mark with a muted performance against Milan.

Milan had failed to win in their previous seven meetings with Barcelona and started as rank outsiders with a team mostly assembled during the course of the season.

Muntari fired a warning shot with a dipping 30-metre volley which flew over the crossbar after five minutes and Stephan El Shaarawy should have done better when he was sent clear by Boateng's flicked pass.

The teenage forward failed to control the ball as he raced towards goal, allowing Carles Puyol to intercept.

From the corner, Boateng hooked the ball just wide of the far post, giving Barca their first scare.

Barca, who could have had a penalty when Dani Alves' whipped cross clearly hit Philippe Mexes' outstretched arm, took control with their familiar slick passing, although they did not create many real openings.

It was Milan who were more dangerous as a low diagonal cross into the area from Zapata eluded El Shaarawy just before halftime.

The second half started with more Barcelona possession before Milan struck the first blow. A short free kick was played by Riccardo Montolivo, his low shot struck Jordi Alba, ricocheted against Zapata's outstretched arms and fell to Boateng to sweep into the goal.

Barca protested furiously and were unsettled as the match degenerated into a niggly affair, with the visitors infuriating by crowd at one point by keeping possession after a drop ball.

Andres Iniesta was close to equalising with a shot which swerved wide but instead Milan added another goal when a well-worked move ended with Muntari firing into the far corner of the net in the 80th minute.

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