From the BBC;
Players from nine La Liga clubs will wear shirts opposing the Super League concept and backing the Champions League when they warm up ahead of their matches this midweek.
Following the lead of Premier League pair Leeds and Brighton, BBC Sport understands Valencia, Cadiz, Osasuna, Villarreal, Alaves, Sevilla, Levante, Athletic Bilbao and Real Betis will wear a specially-designed training top, or a version of it, which states ‘Champions League – earn it’ in England and Spanish.
In addition, there will be messaging displayed on LED boards, on in-stadium screens and virtualised stands as La Liga aim to get their point across.