Both sides had chances in the second period, but it was Barcelona that completed the scoring in the latter stages when Messi converted from close range.
Here, Sports Mole dissects the 90 minutes of action between the two European rivals.
On target: 6
On target: 1
Was the result fair?
There is not any possible situation where anything other than a comfortable Barcelona win would have reflected the events at the Camp Nou this evening. In truth, the home side should have been out of sight at the interval, but Milan had a lifeline when Pique turned into his own net after 45 minutes. The away side had their moments in an entertaining second period, particularly when Mario Balotelli was introduced, but a strong Barcelona performance deserved all the points.
The Spanish champions have been criticised for their approach this season, but it is difficult to find fault with a team that has made an unbeaten start to the season. As expected, they dominated the possession in the Camp Nou, while they created plenty of chances to make the final score more comfortable. It will come as no surprise that there were a few nervy moments in defence, but it was an extremely composed performance from the home side. In truth, they just had far too much for Milan this evening.
AC Milan's performance
The Italian outfit hardly had the ball in the opening 45 minutes, but somehow entered the break at 2-1. That certainly inspired them in the early stages of the second period, you never thought that they were capable of turning the match around. In fairness, they could have been on the end of a real hiding, but picked up a respectable final score in the Camp Nou. The result still leaves them second in the group following Ajax's 1-0 win over Celtic in Amsterdam this evening.
Sports Mole's man of the match
Lionel Messi: Crisis? What crisis? The Argentine had gone four matches without a goal entering this particular match, but answered his critics with a double - taking his tally in this season's Champions League to six goals. The Argentine looked like he had a point to prove this evening, and he made it.
At times, Milan's defending this evening was comical. One of three Barcelona players could have scored the home side's second after poor marking inside the box, while Ignazio Abate's decision to pull Neymar to the ground inside the box cost his side a penalty. They did improve in the second period, but the damage had already been done.
Milorad Mazic had a comfortable 90 minutes in Spain this evening. The Serbian rightly awarded Barcelona a first-half penalty when Abate felled Neymar inside the box, while he was always willing to let the match flow in the correct areas. Just the four yellow cards were issued, meanwhile, with the official sensitive to the nature of the occasion.
AC Milan: Milan will attempt to return to winning ways in the league when they travel to Chievo on Sunday afternoon.
Barcelona: The Catalan outfit also return to league action this weekend with a trip to struggling Real Betis.