Chelsea say a video clip of Conor Gallagher with a young black mascot has been "taken considerably out of context" and condemned the "completely unacceptable" abuse towards the player.
In the widely shared clip, Gallagher does not acknowledge a high five from the child in the tunnel before Saturday's 2-2 draw with Burnley.
The Blues captain, 24, then walks out with the child at Stamford Bridge.
"It's [the abuse] upset me so much," said Chelsea boss Mauricio Pochettino.
"No-one wants to do something like this, with this intention. I think he has many videos and photography with the mascots.