Spain goalkeeper Iker Casillas believes that retaining the European Championship trophy will prove more difficult than winning it in the first-place.

Casillas, 31, who captained Spain to the that success, is fully aware that Spain are now a well-known threat to their rivals – meaning opponents will be better prepared for their threat.

"The problem now is that we are not going to the Euros in the same way as we did four years ago. We were known then, but we were able to gradually surprise people and went on to win the tournament. But now everyone in football knows about Spain," Casillas told reporters on Monday.

However, Spain’s Euro 2008 coach Luis Aragones, believes that Vicente Del Bosque will once again lead the nation to glory, citing the World Cup triumph two years ago as a example.

"I was optimistic at the World Cup and I am again now," the Aragones said. "They are trying to become the only team to win a third consecutive tournament and it will be tremendously difficult. But I think Del Bosque and the team are going to do well. We are favourites and I think we are going to retain it.”

Xabi Alonso, though, agrees with Casillas that his side will need to produce an “almost perfect” display this summer if they are to win Euro 2012 - with the tournament set to be potentially more difficult than their World Cup triumph two years ago.

“It is increasingly more difficult to keep winning,'' Real Madrid midfielder Alonso told GQ magazine. “We have a good team, we have the experience, but there are also other teams that have prepared well and are very eager. I think it will be even more difficult than our World Cup win because we are going to have to do things almost perfectly to win it.''

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