Spain head coach Vicente del Bosque admits his side are not invincible following a lacklustre display against dogged Croatia on Monday night.
The world and European champions struggled against Sleven Bilic's men, but they still did enough to win 1-0 thanks to Jesus Navas' late strike and topped Group C to reach the quarter-finals of Euro 2012.
Del Bosque claimed after the game that he saw a number of positives in his side's display, despite not quite hitting the heights they had hoped to reach.
"In football, nobody is invincible. This goes for everyone and nobody believes differently - not the French, the English, not even the Germans," Del Bosque said in the Spanish base camp of Gniweino in Poland.
"We can lose," he added bluntly as he looked forward to a likely quarter-final either against France or England.
"Four days ago they were eulogising us," said Del Bosque alluding to a 4-0 thumping of Ireland.
"Against Croatia the game was neither bad nor good."
Had the Croatians won the game the Spanish would have gone out given Italy's win over Ireland, which gave the Azzurri the runners-up spot.
Del Bosque insisted Spain were comfortable with their intricate yet high tempo style, saying: "We mustn't have have doubts about it. It would be worse to have doubts.
"We have the resources to deploy against teams who keep it tight.
"I have looked again at the Croatia match and I don't feel as I did at the end - we didn't play that badly.
"We are not overly-optimistic but we have a chance at these Euros," he added.