Sevilla have threatened legal action ahead of Sunday's Spanish Super Cup after a late change of rules cleared Barcelona to use more non-European Union players.
The two clubs are scheduled to play on Sunday night in Tangier, Morocco (3:30 p.m. ET, ESPNEWS and ESPN Deportes), and the Spanish football federation (RFEF) announced one day before the game that the match would have no squad restrictions concerning the use of non-EU players.
The federation's rules normally only allow for teams to register five non-EU and use three in a matchday squad for La Liga games, and Sevilla made their objections clear on Saturday night.
"Sevilla FC is surprised by the RFEF's statement 24 hours before the Super Cup," a club statement said. "It has stated that as many non-EU players as desired can be registered, despite the fact that in their last notice for the 18/19 season, only three were due to be permitted, without exception.
"The Club's legal department is studying the matter and should FC Barcelona submit a team with more than three non-EU players, it would present possible ground for the filing of a complaint on account of an improper line-up."
The BBC reported Sevilla had threatened to withdraw from the game.
Barcelona are expected to have three non-EU players in their squad on Sunday: new signings Malcom, Arturo Vidal and Arthur. Argentina's Lionel Messi and Uruguay's Luis Suarez both have EU citizenship.
The problem appears to lie with Philippe Coutinho, who may still be listed as a non-EU player.
Sources confirmed to ESPN FC on Friday that Coutinho has been granted a Portuguese citizenship through his wife, which would make him eligible to play with the others.
Sevilla could be objecting if the proper paperwork has not been filed to register Brazil international Countino as an EU player.