What you need to know:
- Argentina's two greatest football rivals competing for South America's most prestigious club prize out of the country, and in Spain, has proven controversial, with both clubs expressing their disapproval.
- Boca believe the chaos caused by River's fans means they should be awarded the trophy while River have protested against the loss of home advantage enjoyed by their opponents in the first leg, which finished 2-2.
Boca Juniors striker Carlos Tevez conceded playing a Libertadores Cup final in Madrid on Sunday will be "weird" but rejected suggestions River Plate have been put at a disadvantage.
The second leg was moved to Real Madrid's Santiago Bernabeu after the original fixture at River's El Monumental stadium was postponed last month, following an attack by their fans on Boca's team bus.
South America's football federation, CONMEBOL, ruled River should lose the chance to play at home, with the game moved abroad amid fears of further fan violence.
"It is a weird final," Tevez said Thursday after Boca had trained at Las Rozas, the base of the Spanish national team.
"To play a match between Boca and River in Madrid, it's weird. But as a player, it is important to stay focused on the match."
Argentina's two greatest football rivals competing for South America's most prestigious club prize out of the country, and in Spain, has proven controversial, with both clubs expressing their disapproval.
Boca believe the chaos caused by River's fans means they should be awarded the trophy while River have protested against the loss of home advantage enjoyed by their opponents in the first leg, which finished 2-2.
"We would have liked to have played the game at home," said River goalkeeper Franco Armani on Thursday. "On our pitch, in front of our fans, who deserve it, but the decision is already made. We have to make the best of it."
Both sets of supporters have been allowed an equal allocation of 25,000 tickets for the match in Madrid, despite away fans being banned at Boca's Bombonera ground, as they would have been at El Monumental.
Asked if River's chances had been damaged, Tevez said: "I don't think so. River have a lot more pressure playing at home and now it is 50-50. To play at home, sometimes it goes against you in a Libertadores final."
Security remains high on the agenda after River's fans smashed the windows of Boca's bus and left some of their players injured.
"After Sunday there will be a champion and no more talk," Armani said. "The only thing I can say is that what happened in Argentina cannot ever happen again."
One of Boca's most radical supporters was sent back to Argentina on Thursday after he had arrived at Madrid's Barajas Airport.
"He is one of the most important and dangerous Boca ultras," a spokesman for the Spanish police told AFP.
Tevez also called for calm around the match.
"I think people are smart," he said. "They know they can't mess around here so the truth is everything should happen peacefully, as it should do.
"I think it's important for everyone involved to know that while it is a final, of course, it is a football match. We feel good because we're here and we thank the Spanish people for welcoming us."
Both teams appeared in good spirits as they trained in Madrid for the first time on Thursday.
Boca's players were put through a light session at Las Rozas in the morning before River trained in the evening at Real Madrid's Valdebebas. River had landed at Madrid's Barajas Airport early on Thursday morning.
Attending both sessions were more than 150 journalists while a small number of fans were also seen waiting outside.
Former Boca idol Juan Roman Riquelme voiced his disapproval of the relocated fixture earlier this week, saying it would make it "the most expensive friendly in history".
"It won't be the same. No matter how much I want Boca to win it, I think the final has to be played in our country," Riquelme said.
"The way it is, makes it the most expensive friendly in history."