Real Madrid manager Xabi Alonso revealed that Antonio Rudiger reported being the target of a racist remark following his sides 3-1 Club World Cup victory over Mexican side Pachuca on Sunday.
The German defender appeared visibly upset after the final whistle following a heated exchange with Pachuca's captain, Gustavo Cabral.
Rudiger immediately spoke with Brazilian referee Ramon Abatti Abel on the pitch before heading down the tunnel.
Speaking in his post-match press conference, Alonso confirmed the incident had been brought to the teams attention.
"Toni told us something. We support him, and we will see what happens. I believe FIFA's protocol has now been activated to investigate," Alonso said.