The Wolfsburg midfielder joined Atletico on-loan in August.
"Yes, I'm fine," smiled Diego. "I'm really happy to work here and very comfortable. I am very motivated and my adaptation has been good so far."
Asked if he could sign permanently, the midfielder also told Fichajes.com: "It is too difficult to talk about this, as there's much time still to finalize the transfer and a lot can happen yet.
"I'd rather wait a little longer before we talk about it."