In a repeat of last season's semi-final, the Spanish giants taken on Jurgen Klopp's men and will be hoping for a change in fortunes after a 4-3 aggregate defeat the last time the teams clashed.
The two sides have experienced contrasting fortunes in their domestic leagues in 2013-14, with Real topping La Liga while Dortmund have fallen 23 points behind runaway Bundesliga leaders Bayern Munich.
But Butragueno, who played for the club for 11 years and is now a director, insists Real cannot afford to take their opponents likely.
"We played Dortmund four times last season (they also faced each other in the group stages) and they were very strong," he told Sky Sports.
"I know they're not doing so well in the league this season, but despite that we are convinced they are still going to be very difficult to beat.
"Now we are doing really well since Christmas and I think we are going to reach this tie in good form but you never know."
