A jibe at Manchester United striker Zlatan Ibrahimovic sparked Sunday's derby brawl after defeat to Manchester City.
United boss Jose Mourinho was at the centre of a post-match melee amid claims of City goalkeeper Ederson confronting him after the Portuguese entered the away dressing room.
Marca reports, however, it was City coaching staff which sparked the United anger.
As City players and staff celebrated the win, some members fired a jibe at Ibrahimovic, mocking: "Ibrahim, you talk a lot, but you look a little shaken..."
Upon hearing the taunt, Mourinho demanded greater respect - and this sparked the furious confrontation with Ederson.
Ibrahimovic and some City staff have history from their time together at Barcelona.