Paulo Bento's men sit bottom of Group G and need a convincing win over Ghana in Brasilia on Thursday if they are to have any chance of reaching the next round.
A draw between the United States and Germany would be enough to see both sides through to the last 16.
"Do I believe in miracles? Yes I do. I think it's possible for us," the 31-year-old said.
"We know how difficult it will be but we have to fight. That's Portugal's motto: Always fight. And that's what we're going to do until the end."
The Real Madrid defender – capped 59 times by Portugal - also has no intention of walking away from the national team following his behaviour against Germany.
"I'm not giving up on the Portugal national team," he said. "I will not send my resignation letter like some players did.
"I'll leave when the coach or the president think I can not help anymore. That's something we're going to talk about.
"I want to plan the end of my career better."
