Barcelona vice-president Carles Vilarrubi has warned a returning Jose Mourinho would be "a disaster" for Chelsea.
Mourinho's departure from Real Madrid was confirmed last week by Real president Florentino Perez and the Portuguese is widely expected to return to Chelsea, where he previously won two Premier League titles.
However, Vilarrubi has said Mourinho will not replicate the success he enjoyed at Stamford Bridge when he was last there.
"It is not good for English football," Vilarrubi told The Daily Telegraph.
"Chelsea maybe think they had a good time from him in the past, but you will see the real Mourinho now.
"If he behaves like he did in Spain it will only be an unhappy relationship. A disaster. And at his age he is not going to change."
Mourinho clashed a number of times with Real's rivals Barcelona, particularly former Barca boss Pep Guardiola, but Vilarrubi feels it is more than simply a feud between the two clubs.
"My position is not because he was the coach of a rival, but because of who he is and what he did. His three years in Spain he only creates disagreements, arguments," he said.
"There is nothing positive he brings.
"Apart from his aggression to the coach of Barca, the ambience he creates everywhere he goes, the relations with the players, with the press, are absolutely terrible. I am happy that he is leaving. And so is everyone in Spanish football."
Mourinho will end his third season at Real without a trophy, losing out in the title race to Barcelona and the Copa del Rey final to Atletico Madrid.
In the hunt for their 10th UEFA Champions League trophy, Real were eliminated at the semi-final stage by losing finalists Borussia Dortmund.