The Belgian has already had two years in Madrid.
"I am Chelsea player, but I am happy here," he told AS. "I'll have to see what is best for them but I would be very happy if I stayed here for another year.
"I still haven't spoken to Chelsea though. If I can't play for them, then Atletico is the best club I can be at.
"It would be important for me and the club to make the Champions League next season. I am very happy here."