By ESPNSTAR.com staff
Barring an injury, Casillas will be expected to make his 136th international appearance for Spain and can reach the historic milestone of 100 international victories if the La Roja manage to triumph over Portugal in their semi-finals clash on Wednesday.
The Spanish shot stopper knows he can expect no favours from his Real Madrid team-mate Ronaldo when they go up against each other but asserts that the mercurial forward has not been able to reproduce his amazing club form on the international stage.
The 31-year-old Casillas told Marca: "Ronaldo's season at Madrid was incredible in terms of the way he played, the goals and the records,"
"I don't think that right now he is at his best level."
However, Casillas is aware of Ronaldo's propensity to shoot from far and acknowledges that he will have to be on the alert for any deviation in the flight of the ball due to the unique way Ronaldo strikes it.
"The ball does something strange," he told Marca, adding that those being used at Euro 2012 did not bend and swerve as much as the "Jabulani" used at the World Cup two years ago.
"It doesn't quite reach those extremes but if you give it a good whack it always swerves in a deceptive way," he said. "I'll have to be on my guard."
Casillas's international teammate Gerard Pique agrees that the Spanish will have to pay attention to Ronaldo, but is also wary of another Portuguese menace in the form of Nani.
"Nani is a player with a lot of quality in one-on-one situations," Pique told Reuters.
"He can pop up on the right or the left and is a born goal scorer with a powerful shot.
"We will have to use all the weapons in our arsenal to stop him and Ronaldo."
Spain last met Portugal in a competitive match at the 2010 World Cup and won that close encounter 1-0 courtesy of a David Villa strike but it was the introduction of Athletic Bilbao striker Fernando Llorente that swung the game in their favour and Pique believes Llorente will be able to make a similar impact this time round.
"He used his power in the air to great effect and fought like a lion,"
"He could be an option for Wednesday and he is training very, very well," added the 25-year-old.
"He is one of the players who have yet to feature but for sure he will get his chance and that could be against Portugal."
Spain and Portugal have faced each other 34 times so far with the Spanish winning 16 of those encounters and the Portuguese only managing 6 victories over their Iberian neighbours.