The former Castilla star is being lined up by Real management for a return this summer.
Mascarell revealed to Efe: "I know that my representative is in contact with Real Madrid.
"The club knows very well that I am happy in Germany, and from there, the club will make a decision and we will find the most satisfactory option to continue to progress.
"I come from Real Madrid, I grew up and playing with Madrid is a dream that will hopefully be realised. But I'm 25, and I have many years ahead of me. What I want is to feel important in a team. I found that in Germany."