Barcelona started the season by winning the Spanish Super Cup, but weakness in defense is expected to be a major problem in the face of Milan.
Striker Milan Zlatan Ibrahimovic will return to the Nou Camp for the first time since out of Barca last season.
Barca defender Carles Puyol can be lowered again for the first time since knee surgery in May lalun yet another defender Gerard Pique is still injured, so Eric Abidal is expected to fill the void behind.
"We have to play better with better preparation," said Barca coach Pep Guardiola after a draw against Real Sociedad.
Meanwhile, Milan are ready to reverse predictions of many people who do not favor the Rossoneri when clashing with Azulgrana in the first matchday of Group H Champions League.
"With the talent we have, I believe it can create problems for Barcelona," Allegri said in a press conference at Camp Nou.
To reduce Barcelona game, Allegri asserted would not play defense. The coach who brought Il Diavolo won the Scudetto last season, will apply the pattern of attacking play to get maximum results.
"Playing defensive against them could be a problem. We have to play seriously. Regardless of the tactics and techniques, we have to play brave, "he said, as quoted by Goal, Tuesday (13/09/2011).
"I can not wait for the team that we would see on the field tomorrow (early morning-red). We are the Italian champions with players who are used in this match, but we'll see what happens, "added the 44-year-old coach.
About Zlatan Ibrahimovic's absence due to injury, Allegri will likely decrease as a striker Alexandre Pato supported by Kevin-Prince Boateng from the middle row.
"Pato and Boateng will be lowered. I will lose one attacker, but do not know who because of injury Ibra very suddenly. "
