Barca earned a 1-1 draw at the San Paolo, but Gattuso insists they're capable of winning at the Nou Camp.
He said, “Naturally, qualification is wide open, we will have time to prepare for the second leg and know they will be missing Sergio Busquets and Arturo Vidal, as they'll be suspended.
“The error on the goal we conceded was Mario Rui broke the defensive line and Maksimovic was meant to get back there, but instead we didn't time it well and left a gap.
“In possession, we tended to win back the ball and then get it back to where we started from, whereas we should've pushed it forward or across to the other flank.
“If you are in the right position, Barcelona can press all they like and it won't make a difference. It's true that having Messi running at you can cause problems, but we still missed something in terms of quality this evening."