The allegations come from Serhat Pekmezci, the former head of scouting at Fenerbahçe and the man credited with discovering Guler.
Pekmezci claims a clique of stars with "very high egos" is deliberately freezing the Turkish international out, systematically isolating him within the squad.
Guler joined Madrid in 2023 but has struggled to secure a regular starting place. While his limited role has often been attributed to injuries and competition for spots, Pekmezci insists the problem is personal rather than performance-related, with senior figures actively blocking his progression.
According to Pekmezci, Guler's stagnation is not due to a lack of ability; established stars are refusing to integrate him into the team.
He suggested that the transition following the Toni Kroos and Luka Modric era was meant to support Guler's rise, yet the current dressing room dynamic has hindered it.
Pekmezci added that this toxic environment also contributed to Xabi Alonso's shock departure from the Bernabeu.
"Arda Guler is being subjected to mobbing [bullying]," Pekmezci told Sports Digitale.
"It's not that he complained to me, but he knew this would happen. I told him to be patient.
"The harassment came from the players. There is a group there that has not been able to accept Arda; unfortunately, they are players with very high egos."