The Spain international believes that Zlatan Ibrahimovic will be the Rossoneri's biggest threat and wants to keep him away from the penalty area
However, Puyol insists that his side will not adopt a defensive approach following the goalless draw in the first leg.
"This is the most important match of the season," Puyol told reporters at a press conference. "This is a final, there is no margin for error.
"It is always important not to concede any goals. We will have to move the ball quickly, keep a high pace and score as soon as possible.
"We can only play one way, which is attacking from the first whistle. And if we score, we will try to score even more, while remaining vigilant."
Puyol then identified Zlatan Ibrahimovic as the Rossoneri's main danger man ahead of Tuesday's crunch clash.
The Sweden international will return to Camp Nou for the first time since he left the Blaugrana in 2010, and the Spain defender admitted that Barca will have to be extra careful with the 30-year-old.
"You cannot stop him physically, and technically he is very good," Puyol said. "We have to keep him away from our area so that the ball does not get to him and he can only shoot from distance.
"But the task of marking him does not belong to just one player, but to the entire team."