The Brazilian re-joined the La Liga giants from Chelsea at the start of the season but Atletico’s transfer ban meant the move was only made official on January 1.
That has meant the Spain international has had to make due with just training sessions and friendly matches, leaving him eager to return to first-team football.
And, speaking at his unveiling at the Wanda Metropolitano this week, Costa said: “We were eliminated from the Champions League, which was bad luck, but we still have a lot to do this year and we are going to fight for everything we can achieve.
“I am feeling a lot better than when I arrived. I have prepared well and I am anxious to play and do what I need to do, which is to help the team and score goals.
“I have been waiting a long time for this moment. I am tired of training, I want to play.”