LOS ANGELES — Running back Anthony Brown has quit Southern California’s football team, and coach Steve Sarkisian was stunned Thursday by Brown’s apparent accusations of racism against him on social media.

A photo of the words “Couldn’t play for a racist man!!!!” was posted on what USC said was Brown’s Instagram account. The posting was later deleted.

“Sark treated me like a slave in his Office,” was posted in the caption to the photo, along with the hashtag “Fighton.”

Sarkisian was told about the apparent posts from Brown, who is black, shortly after USC finished practice Thursday. The visibly disturbed coach called them “ridiculous,” saying Brown had shown no indication he felt slighted or insulted in their relationship.

“If you ask anybody in our building, any of our players ... that’s about the furthest thing from the truth,” Sarkisian said. “Quite honestly, I’m shocked.”

Brown is a senior who played cornerback for the Trojans until this year, starting two games in each of his first three seasons. He played in only two games last year due to ankle injuries.