Diaz has moved across the Spanish capital after five years at Getafe in a one million euros move with fans' favourite Dominguez headed to Borussia Monchengladbach for eight million euros, but the Argentinian is relishing the challenge of moving up a level in terms of expectation at Atleti.
He told AS, "He (Dominguez) has played here, come through the academy and is important for the club but I have come here to do my bit and I have the same pressure all players have when they arrive at a new club. I don't think that my coming here and Dominguez leaving will bring me more pressure than the others.
"When a team like Atletico became interested in me I wasn't in any doubt. I am arriving with a lot of desire and happiness. I want to demonstrate that on the pitch because with words I can't say very much. I hope it will be a good year for the team."
Diaz is also looking forward to working with his compatriot Diego Simeone who guided Atleti to the Europa League title within six months of taking charge of Los Colchoneros.
"Once the training sessions begin I will get to know him more. I have spoken to him a couple of times but I don't know him as a coach yet. I don't have any doubt over his capabilities and I am very happy that he could be my coach.
"I think that if a manager and his team bring you to a big team it is because for them you are an important part of the project. "