Barcelona forward Lionel Messi has warned of Real Madrid\'s rapid counter-attacking threat as the arch-rivals prepare for a Sunday showdown. While praising Real Madrid\'s game, the 25-year-old Argentinian refused, however, to comment on their coach Jose Mourinho, explaining that he had never spoken to him. \"Madrid kill you in the counter-attack,\" Messi said in an interview with El Pais. \"They have very fast forwards and the connection between defence and attack takes five seconds and then it\'s a goal. They don\'t need to play well to score three goals. They have a lot of positions for their players who are very good.\" Messi said he was friends with two fellow Argentinians in the Real squad - Gonzalo \"El Pipita\" Higuain and Angel di Maria. \"You don\'t see El Pipita and then he has two kicks and scores twice,\" he added. The triple FIFA Ballon d\'Or winner declined to give his opinion of Mourinho, however. \"I can\'t say anything. I don\'t know him, I have never spoken to him,\" Messi said. \"I can only comment on what he has achieved, which is a lot, many titles. I know his players speak well of him but I don\'t know him.\" Barcelona, who lead La Liga, with an eight-point gap over sixth-placed Real, will face their rivals at the Camp Nou on Sunday. Messi said he could remember every win over Real. \"Beating Real Madrid is the best because of the significance, they are a very good team,\" he said of a clash between Spain\'s footballing giants that transfixes the nation and is known as El Clásico. FIFA