LA Galaxy defender Robbie Rogers said in a post on his Facebook page that an opponent repeatedly called him an anti-gay slur in his return to action with the club's reserves against USL side Orange County Blues.
Rogers is an openly gay player in Major League Soccer, having come out four years ago. He is returning from a serious injury that required ankle surgery that saw him miss the last two-and-a-half months for LA.
He did not name the opponent who targeted him during his rehab stint with LA Galaxy II. The 29-year-old said it was the first time he had suffered any abuse during a game since he came out.
In the Facebook post, Rogers wrote: "In the heat of the last 15 minutes of the game a player from the opposing team called me a 'queer' repeatedly. To be honest my initial reaction was one of shock.
Rogers went on to write: "Minutes later my head was back in the game. And this morning even most of the anger has faded and the predominant emotions left are just love and gratitude.
"But mostly I'm proud of myself. I am proud more than ever that I had the courage to come out as a queer man. I feel so fortunate to have gotten to share my story with others and to have gotten to play this sport I love so much as an openly gay person."
On Sunday evening, MLS and USL released statements, announcing that they would investigate the incident and reiterating its "zero tolerance for homophobia."