Chelsea pair David Luiz and Ramires reportedly informed John Obi Mikel that referee Mark Clattenburg had used racist language while speaking to the midfielder during the Blues' defeat to Manchester United on Sunday.
The Premier League official is under investigation by police after it was accused that the 37-year-old's language towards Mikel had contained a racial element.
It is believed that Mikel was unaware of the initial comments but was told by Luiz and Ramires, who are thought to have heard the alleged slurs during Chelsea's 3-2 loss to United, according to the Daily Star.
Reports have claimed that Mikel confronted the match official with manager Roberto Di Matteo and chief executive Ron Gourlay after the game, which is believed to have grown into a heated exchange.
The Football Association are also investigating a complaint made to the Premier League from the Blues regarding alleged "inappropriate language" used by Clattenburg towards Mikel and Juan Mata.
