Spain coach Vicente del Bosque said Tuesday that no team is invincible as his side look to defend their European Championship title.
The defending champions looked well off their usual exhilarating form as they struggled Monday to see off a dogged Croatia 1-0 - though they still did enough to win Group C and reach the quarter-finals of Euro 2012.
Del Bosque said afterwards his side had not reached the heights as they thanked a late effort from reserve striker Jesus Navas for their win.
"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,: he insisted, adding that all teams had Spain's respect."
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 and "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," he insisted further.
"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," he told reporters, adding that media talk in Italy of his side making a pact with the Croatians for a high scoring draw that would have put the Italians third and out was an added unwelcome distraction beforehand.
Some observers in Spain believe Del Bosque should rotate his squad more - especially in attack where he has relied on Cesc Fabregas as well as Fernando Torres - both have responded with two goals each, although it was Navas who finally made the difference on Monday after replacing Torres.
"Football is a permanent debate. We have 23 players and all of them can feature. People's tastes are different," said Del Bosque while stressing that Spain had a stable philosophy of how to play and all the squad worked on that basis.
Confidence remains high, Del Bosque said - as well it might for a side which has won the last two major tournaments - although none has even won three in a row, their goal here.
"We are not overly-optimistic but we have a chance at these Euros," he observed, while insisting he was not about to change the way the side plays by indulging in the "luxury" of extra strikers from the outset - even though " I too would like more people in attack.
And Del Bosque said he was quite happy to take on sides who play it tight and try to close down space as "we have intelligent players to deal with these situations.
"It saves more on energy than when you have to play across the whole pitch" against more cavalier opponents.