Barca host United defending a 1-0 lead for their quarterfinal tie.
"There is no fear, only tremendous excitement," Valverde said in his pre-match press conference.
"We're ready to try to go through, knowing that we're facing a great team.
"We're both good sides, we have a lot of excitement to try to reach the semi-finals.
"I think that experience [of the Roma loss] serves for something.
"We all know we're in for a tough game.
"They could go through as well, but we have to do everything possible so that they go out because of us."
Some have suggested that, with their 1-0 lead from the first leg, Barcelona will prioritise defending that lead over anything else.
"Evidently, we'll try not to concede and also try to score," Valverde said.
"Our priority is scoring, not going out there thinking we have an advantage.