Augsburg defender Juma Bah was "subjected to utterly vile racist abuse and death threats" on social media after receiving a red card in the 1-1 Bundesliga draw with Union Berlin on Saturday, his club said on Instagram.
According to Augsburg, Bah's family was also threatened. The team said it will report the incident to the police and pursue all legal options available.
"We are appalled by this hatred. And we want to make one thing absolutely clear: We will never accept, tolerate or simply ignore such behaviour!" Augsburg wrote.
Bah was sent off in the 63rd minute for a reckless tackle. Before that, Union's Felix Uduokhai had also received a red card.
The player moved to Augsburg in September on a loan from Manchester City.
"Anyone who racially abuses or threatens one of our players is not only attacking an individual, but also the values of our entire FCA family," the club said.