Ter Stegen's future at Barca is in doubt after the arrival of Joan Garcia from Espanyol.
Asked about the German veteran, Deco told La Vanguardia: "I don't have to talk to him. My job is to build the best possible team for the coach. It's not something that concerns me.
"Furthermore, there is no contract that says a player has to play. From then on, it's the coach who makes the decisions, and each player has their own ambitions."
Deco also explained: "We have made the decision to sign a young goalkeeper, which means he can play tomorrow, stay on the bench or play in a year or two. We have expectations of Joan that will then have to be confirmed.
"Everyone who comes here starts from scratch, no one comes with an advantage over the others. I have great respect for Marc (Ter Stegen), but with Joan we had to make a decision for the present and the future. It will be the coach, therefore, who will have to decide.
"When a player really wants to leave, it is very difficult to stop him. But that is not the case at the moment."