One of Barcelona's president Joan Laporta's objectives is to reduce the wage bill at the club. Various players have exorbitant salaries and the club have engaged in talks to bring them down, such as with Gerard Pique, Sergio Busquets and Frenkie de Jong, among others.
As part of those negotiations, both parties have to reach an agreement. However, per Casena SER, there is a contractual requirement that could allow Barça to unilaterally adjust some contracts.
Barça can knock 10% of a player's salary if they don't participate in promotional events for the club. If the players in question miss three events throughout the season, said reduction can be imposed.