The Rossonerri are drawn with the reigning European champions in Group H alongside BATE and Viktoria Plzen.
Speaking ahead of their clash with Pep Guardiola's men on 13 September at the Nou Camp, Allegri believes his side can neutralize their threat.
"The most important thing will be to limit the sources of Barcelona's play," the Italian coach is quoted as saying by Il Corriere dello Sport.
"Barcelona though are a team that you can put into difficulties by attacking them which is what Porto showed in the European Super Cup."
Allegri went on to switch his focus on Milan's Serie A opener against Lazio which is expected to go ahead following a proposed agreement to call of the recent strike.
"Now we have to think about the league which will be open and elevated towards the highest levels," he said.
"It will be an interesting championship."
Milan, without its players on international duties, will play a friendly against Como on Friday.