Barcelona have been fined 602 euros (£503) after Atletico Madrid complained about the club’s approach to striker Julian Alvarez.
Atletico said their La Liga rivals contacted the Argentina international without first notifying them in writing.
The 26-year-old stayed with Atletico and remains under contract until June 2030. The fine was imposed by the Spanish football association.
Atletico also referred the matter to Fifa, but football’s world governing body said it did not have jurisdiction to deal with the case.
Alvarez has been booed by Atletico supporters on several occasions this season. However, some fans gave him a standing ovation after he scored the winning goal in Saturday’s victory over Deportivo La Coruna.
The result moved Diego Simeone’s side to within two points of Barcelona at the top of La Liga.
After the match, Alvarez apologised to Atletico’s supporters for comments he made in an interview during the summer, when he said he wanted to “fulfil his dream” of playing for Barcelona.
“It was a mistake. I understand why the fans are angry,” said Alvarez.
“If I were a fan, I’d be angry too. Especially given how they’ve supported me since I arrived.”
Alvarez joined Atletico Madrid from Manchester City in August 2024 on a six-year contract. The transfer was worth up to £81.5m.
He scored 36 goals in 103 appearances for Manchester City before moving to Spain. Since joining Atletico, he has scored 51 times in 115 games.
