The 45-year-old coach says Milan will need to improve on their display of three weeks ago to eliminate a Barcelona team thirsty for revenge on Tuesday night
The Italian giants go to Camp Nou leading 2-0 on aggregate courtesy of goals from Kevin Prince Boateng and Sulley Muntari.
But, despite the advantage, the 45-year-old is aware of the threat the Blaugrana possess and has stressed the importance of improving on their performance in the first leg.
"We will play against a team that will fight to overturn a two-goal deficit, so we must perform better than in the first leg," he told reporters at a press-conference.
"Last year, when we met them in the group stage, Barcelona played with three defenders. We have to be better in defence tomorrow and manage the ball a lot better than we did at home."
The former Cagliari coach also noted the differences between the two European giants and believes a three-pronged attack is the key to victory.
"Italian football is different to other European leagues. Barcelona always force their opponents to play the same way because of their ball possession," he added.
"If we can keep Barcelona away from our box, then we have a better chance of qualifying for the quarter-finals. We will play with three forwards tomorrow."
If Milan are successful in Camp Nou on Tuesday night, they will discover their quarter-final opponents on Friday, March 15.