The Westphalians need to go one better than the 4-1 victory over the Spaniards in the home leg of last season's semi-final if they are to keep their hopes alive of reaching a second successive final this year.
Although they were outclassed and outplayed by Carlo Ancelotti's men at the Santiago Bernabeu, Klopp says the remaining 90 minutes in the tie will be different, and that the final word has not necessarily been said in their Champions League campaign.
"There are two games in this quarter final - one in Madrid, and the other in Dortmund," he said on his club's website.
"I am far less critical than my players, who are all sitting with heads drooped in the dressing room.
"We had many chances and could have scored four or five goals. We just made mistakes and got punished - Barcelona also conceded three goals here.
"We can learn from this game. We weren't cool enough and lacked the belief. We didn't make things uncomfortable enough for them."
In spite of Klopp's reluctance to concede defeat, Dortmund know they will have to write history at home to reach the last four.
"Let's say we've been in better situations and we're not really in any kind of position to lay down the gauntlet to them, but we have a duty to give it everything," Klopp added.
"We will do that because there is always a glimmer of hope.
"First, let's get a positive result against Wolfsburg on Saturday, and then we'll mobilise the troops for the return."