"We're facing a very strong team, with the semi-finals at stake for another season," he told UEFA.com on Tuesday. "We're playing at home and we have a [first-leg] result that isn't too bad, but we'll have to give a practically perfect performance to go through.
"This game will be serious. We have to handle it properly, every part of it, but we must also match the intensity and ambition we showed against Milan. When we play like that, our opponents suffer a lot.
"Tomorrow isn't as demanding (Barcelona trailed Milan 2-0 after their round of 16 opener at the San Siro), but we still need to perform. Unfortunately we don't have a full squad, which weakens us, but the team will play as if it were the final."
Barcelona reached the semi-finals of the competition last season but lost to Chelsea.