Spain's hopes have been rocked by their opening group defeat to Switzerland.
"It's obviously a setback," Reina told Liverpool's official website. "We're obviously really disappointed, but we have two games ahead and if we win them I think we'll go through.
"So now we have to focus on getting ourselves ready for the next game.
"We knew that any opponent here was going to be tough, and maybe this was good for us to lose now, so we pay a bit more attention and wake up a little bit for the future games.
"I think one thing is clear - we didn't deserve to lose. Unfortunately we did.
"But the team played good football, we made a lot of chances and it was just one of those games.
"It was more or less like the game we played a year ago against the USA in the Confederations Cup. We have to react and win the next two games."