La Liga ambassador Fernando Morientes has urged Barcelona's players to form a guard of honour for Real Madrid before Saturday's Clasico at the Bernabeu.
Madrid defeated Gremio 1-0 on Dec. 16 to win the Club World Cup, and two lines of opposition players welcoming a newly crowned champion onto the pitch is a custom in Spanish football.
Cristiano Ronaldo said last week in Abu Dhabi that he thought it would be a "nice" gesture, but the 'pasillo' is not mandatory, and Barcelona director of institutional relations Guillermo Amor has said it would not be appropriate on this occasion given La Liga is a completely different competition to the CWC.
Morientes, who made 182 appearances for Madrid between 1997 and 2005, told Marca: "I believe it is an unwritten law. Nobody can make anybody do a guard of honour, but it is about manners and respect.
"That is the best way to speak to the younger generations. If Madrid had to do it, I would do the same. There is a lot of rivalry, but also a normal natural relationship.
"The image in the dressing-room, of them all shaking hands, which is not seen, is important. Then on the pitch there are no friends, they all want to win."
Madrid go into the game 11 points behind leaders Barcelona in the La Liga table with a game in hand, and Morientes said that his former teammate Zinedine Zidane's side realistically must take three points to keep their hopes of retaining the title alive.
"Madrid need to win, nothing else," he added. "They must go out in the game with this mentality, as a Barca victory would make things very difficult. Nothing cannot be saved, but it is important to reach February with a chance."