Borussia Dortmund defender Mats Hummels has underlined the importance of keeping a clean sheet against Real Madrid in the Champions League on Wednesday.

The German club will host the defending Spanish champions in the first leg of their semi-final tie at Signal-Iduna Park.

"We know how difficult it will be to come out on top from these two games, yet we also know that anything is possible for our team," he told the club's official website. "A win and a clean sheet are important because then every goal we score in Madrid will work to our advantage.

"Real Madrid are a lot more than Cristiano Ronaldo and have top players in every position, but that partly applies to us as well. It will be crucial to attack and defend as a team. If all 11 players have the same mentality, we are very difficult to beat."

The second leg will be played at the Santiago Bernabeu in Madrid next week.