The German club will host the defending Spanish champions in the first leg at Signal-Iduna Park on Wednesday.
"We're expecting a very tough game," he told Bundesliga.com. "I think Real have improved a lot since we played them in the group stages, but we've got nothing to lose.
"We've had a terrific Champions League campaign so far, which is why we're determined to get a good result against Real.
"We want to win but a goalless draw wouldn't be bad. Against Malaga [in the quarter-finals] we saw for ourselves just how difficult it can be at home after a 0-0 draw in the first leg."
Madrid failed to beat Dortmund when the sides met twice in the group stage of the competition earlier this season.