Diego has been linked with a move to Atletico this season.
"The problem isn't the money. Money will not be a fundamental factor for if I stay or go," he said.
The ex-Atléti player looks back on his time at el Vicente Calderón positively, and is grateful for the support he received from the fans: "It's fantastic for a player to know the affection and respect they have for me. I have always said that I have a soft spot for Atlético. They were nine wonderful months, but now I am here and we are at a very important moment."