Spain coach Vicente Del Bosque said Wednesday his titleholders must be on their guard as they prepare to face France in Saturday's quarter-final showdown.
The two countries met in the last 16 at the 2006 World Cup and the French won, since when Spain have been unstoppable.
"I retain an image of the 2006 World Cup. We under-estimated the French as they were getting on. It is a very Spanish trait not to pay attention to one's rivals," added Del Bosque.
"France were the most complicated opponents for us, the strongest in Group D. they have the ingredients of a strong team.
"Technically they are strong and very organised.
"I think they'll play like us - the French do not have any complex."