Southampton have contacted Hampshire Police after teenage midfielder Alex Jankewitz received racist abuse on social media.
“Abuse of any form will never be tolerated at Southampton,” the club said in a statement.
“Supporters who stoop to such abhorrent and archaic standards are not welcome as Southampton supporters or anywhere else within football.”
Swiss Jankewitz, 19, was sent off two minutes into his full debut for a tackle on Scott McTominay. Southampton finished with nine men after Jan Bednarek was also dismissed late in the game.
The statement added: “The club is passing on all abusive messages to Hampshire Police and hope they are able to permanently remove those individuals from our football community.”
This latest incident of racist abuse directed at a footballer on social media is one of several to have been reported over the past few days. United and England forward Marcus Rashford said he received abuse on Saturday.
Culture Secretary Oliver Dowden told BBC Sport on Wednesday that the UK government would consider fines for social media companies if they did not tackle the problem.