Sevilla say they could withdraw from Sunday’s Spanish Super Cup if opponents Barcelona name more than three non-European Union players for the match.
The Spanish football federation announced on Saturday there were no restrictions on non-EU players as it classed the game as “not professional”.
Only three non-EU players are allowed in each La Liga matchday squad.
It had been thought the Spanish Super Cup was the same but Sevilla said they would object to “an improper line-up”.
The annual match pits the La Liga champions against the Copa del Rey winners. Because Barcelona won the domestic double last season, Sevilla qualify as Copa del Rey runners-up.
The match is being played in Tangier, Morocco, and will be contested over one leg for the first time.
A Sevilla club statement read: “Sevilla FC is surprised by the RFEF [Spanish football federation]’s statement 24 hours before the Super Cup.
“It has stated that as many non-EU players as desired can be registered. In their last notice for the 18-19 season, only three were due to be permitted, without exception.