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. ''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. ''If you ask anybody in our building, any of our players ... that's about the furthest thing from the truth,'' Sarkisian said.