Gerard Pique was whistled by fans when the Barcelona defender took part in a Spain training session on Monday, as political tensions in the country continue to spill into sport.
Barca played out a 3-0 victory over Las Palmas at an empty Camp Nou on Sunday, amid unrest in the region surrounding Catalonia's independence referendum.
Barcelona president Josep Maria Bartomeu made the call to keep supporters at the gates after La Liga refused to sanction a postponement, describing his decision as a "rejection of what has been experienced", while the stadium scoreboard bore the message "Democracia", featuring an illustration of a ballot box.
Pique has been vocal in his support of Catalonia's attempts to secede from Spain, prompting a backlash from those who fall on the other side of the argument.
Vídeo 360°: así reaccionó el público cuando Piqué saltó a entrenar con la selección española. "España es tu nación". 360° video: that's how the fans in Madrid reacted when Piqué started the training session with Spain. "This is your nation". Posted by Alberto Piñero Goal on Monday, 2 October 2017
The 30-year-old, who has won the World Cup and European Championship, even offered to retire from international duty if coach Julen Lopetegui considered his presence a "problem".
And tensions ran high in the capital Madrid as Pique's entrance to the pitch was jeered, while some in attendance lifted banners with inflammatory messages towards the defender.