Juventus manager Massimiliano Allegri has warned his side that they cannot afford to simply protect their three-goal lead when they visit Barcelona for the second leg of their Champions League quarter-final tie on Wednesday night.

Juve are the favourites to progress into the semi-finals courtesy of their convincing first-leg victory in Turin, but have reason for caution after seeing Barca pull off an even more miraculous comeback to overcome Paris Saint-Germain in the previous round.

Allegri believes that his side will need at least one away goal to strengthen their position, leaving Barca requiring five to pull off an aggregate victory.

"We need to keep our heads and find a way to score at least once," he told reporters.

"We have huge respect for Barcelona and we know that we will need to play even better again to go through."

Juve have conceded just two goals in their nine Champions League outings so far this season.