The Atletico Madrid star is Brazilian born and raised, but will turn out for Spain in his homeland.
"The criticism does not affect me," he said. "If I'm playing at a World Cup, I'm prepared to suffer pressure on the pitch.
"It's always been my dream to play in a World Cup, even when I was a kid. I used to watch Ronaldo - 'O Fenomeno' - all the time. He was my idol.
"It's true I could have been playing for Brazil at this World Cup. But Spain is my country now and the people are with me. "It's not a problem for me if people think Diego Costa has caused a controversy. No one can accuse me of showing Brazil a lack of respect.
"I am a professional but my choice to play for Spain was made with the head. I don't regret it. Brazil approached me very late in my career. I played in Spain for many years but only recently did they think of me. When Spain approached me my choice was clear. I am a 'naturalised' player. But those have merits too and deserve their chance.
"Spain have given me a chance to show how good I am at this World Cup and I am convinced I can make an impact."
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