Referee Antonio Mateu Lahoz has been ruled out of Saturday's clash between Real Madrid and Barcelona, and his replacement could raise a few eyebrows.
Experienced whistler Lahoz had been assigned El Clasico but on Friday it was revealed he is suffering with a muscle injury, with Jesus Gil Manzano named to take on the job instead.
The 44-year-old Lahoz officiated in Wednesday's Champions League clash between Bayern Munich and Paris Saint-Germain.
The Spanish Football Federation (RFEF) announced: "The refereeing committee for professional competition (CACP) has changed, due to a muscle injury, the appointment of referee Antonio Mateu Lahoz, the referee initially appointed to direct the match between Real Madrid and Barcelona on matchday 30 of the Primera Division. His replacement will be Jesus Gil Manzano."
Manzano is the referee who showed Barcelona captain Lionel Messi the first red card of his club career in January's Supercopa de Espana final defeat to Athletic Bilbao.
Messi swung an arm at Asier Villalibre in the final moments of extra time, and the Argentinian was dismissed following a VAR review.
Barcelona boss Ronald Koeman refused to discuss the referee after that match, saying: "It's better if I don't talk."
Manzano also previously red-carded former Barcelona superstars Luis Suarez and Neymar during their Camp Nou careers.
Speaking at a pre-match news conference, Koeman said of the referee change: "I think we talk a lot about referees sometimes.
"The referee decides according to what he sees, with the help of the VAR. So I don't care who the referee is. I just hope the referee does a good job."