The visitors jumped to a 2-0 lead before Barca fought back to earn a draw for the first-leg of their Champions League semifinal.
Cubarsi said afterwards, "We didn’t come out the way we should have. We were two goals down, but the team’s mentality allowed us to equalise and then we conceded another goal, so we have to improve on some aspects.
"We’re going to go to their stadium with a 0-0 draw and win."
"I could never imagine this"
Cubarsi, 18, also had time to reflect on last night's experience.
He continued: “I never imagined that at my age I’d be playing in a Champions League semi-final with the club of my life, but I’m handling it very well.
"My family is helping me with everything, and so are the fans who are completely behind us.
“They got at us very little, we have to improve in some details, but we don’t have to be negative either.”