Lionel Messi ended one of his leanest scoring runs in years with a two-goal performance on Wednesday that guided Barcelona to a 3-1 victory over AC Milan and into the knockout stage of the Champions League.
Messi scored a 30th-minute penalty for his first goal at the Camp Nou Stadium since Sept. 24 before Sergio Busquets doubled Barcelona's lead with an angled header nine minutes later.
An own goal by Barcelona defender Gerard Pique made it 2-1, but Messi sealed the win after finishing a combination with Cesc Fabregas in the 83rd.
Barcelona secured a place in the next phase thanks to Ajax's 1-0 victory over Celtic.
Barcelona leads Group H with 10 points, Milan has five points, Ajax has four and Celtic is bottom with three.
"Leo played a phenomenal game. He was sharp, showed quickness and was better one-on-one," Barcelona coach Gerardo Martino said.
Messi has struggled following an injury-riddled October, going four league games without a goal for the first time since the 2010/11 season.
And while the Argentina forward still does not appear to be 100 percent fit, his finishing touch in front of goal remains unflinching.
Milan, meanwhile, can take a few positives back to Italy, where it is trailing badly in the Serie A title chase.
"Barca is always Barca and they showed they were a stronger team tonight. But we played a good game," Milan coach Massimiliano Allegri said. "I'm not sure what will happen with my future. We have to win our next league game and there is still much to play for in the Champions League."
Mario Balotelli watched from the bench as Robinho and Kaka led Milan's attack, which appeared to be nonexistent until after Messi's opening goal.
Most of the opening 30 minutes were played in Milan's half, but Barcelona failed to create any real danger before Neymar went down under the weight of Ignazio Abate's hand. Messi then blasted his spot kick past Christian Abbiati for his first goal since a 1-1 draw at Milan in the last round.
Milan's defensive line was in a shambles as Busquets rose unchallenged to meet Xavi Hernandez's free kick with a header past Abbiati.
Barcelona seemed ready to run away with it until Kaka burst past Dani Alves and had his pass turned into the net at the near post by Pique.
Balotelli replaced Robinho to start the second half as Milan raised its game, with the Italy striker picking out Kaka's run in the 64th minute - only for the Brazilian to poke the ball wide from the outside of his foot.
Messi was troubling Milan with his dribbling runs but his usual quickness was not there. Still, the Argentine forward did provide Andres Iniesta and Alexis Sanchez with great scoring opportunities, forcing Abbiati to make some key stops.
Neymar was also a threat and surged past three Milan players in the 73rd minute only to shoot wildly over goal.
Messi made no mistake after Fabregas played the ball into his path as he burst through the Milan defense to score his sixth goal of the competition.
"Barcelona's obligation is to always be the best in every competition," Martino said. "So to qualify after four rounds is reassuring."