AC Milan's Thiago Silva (R) dances with teammate Alexandre Pato as they celebrate his goal against Barcelona in the final minute to equalise during their Group H Champions League soccer match at the Nou Camp stadium in Barcelona Sept 13, 2011. [Photo/Agencies]

* Pedro, Villa score after lightning Pato strike

BARCELONA - Thiago Silva powered home a header in the second minute of stoppage time to steal a 2-2 draw for AC Milan at holders Barcelona in the heavyweight pair's Champions League Group H opener on Tuesday.

Barca had recovered from conceding the fifth quickest ever goal in Europe's elite club competition, scored by Alexandre Pato after 24 seconds, through strikes from Pedro and David Villa.

Once ahead they quickly settled into a rhythm, enjoying almost 70 percent of possession, but failed to kill off the seven-times champions and surrendered the lead for a second consecutive game following Saturday's 2-2 La Liga draw at Real Sociedad.

Barcelona's Andres Iniesta (C) grimaces after being tackled by AC Milan's Alessandro Nesta (L) during their Group H Champions League soccer match at the Nou Camp stadium in Barcelona Sept 13, 2011. [Photo/Agencies]

Their disappointment was compounded by the news that midfielder Andres Iniesta will be out for around four weeks after tearing a leg muscle shortly before halftime.

"It wasn't easy trying to penetrate the opponent's penalty area crowded with eight defenders," Barca coach Pep Guardiola told a news conference.

"We tried but at the end they levelled from a corner. What Milan did has a lot of merit. They made it as far as our goal two and a half times and they came away with a point."