The 22-year-old played no part in La Roja's 5-1 defeat to Netherlands in their Group B opener on Friday, but has been tipped to feature in Wednesday's clash with Chile.
"I'm relaxed. Proud, given all that I'm doing and I really want to win things," he said in an interview with Adidas.
"I want to have a big role in this World Cup, should I get the chance to play and help my teammates, who are desperate to lift the trophy again."
Koke helped Atletico win their first La Liga title since 1996 last term.