San Diego Loyal midfielder Collin Martin said it was "truly moving" when his team-mates left the pitch in protest following an alleged homophobic comment aimed at him.
Junior Flemmings from Phoenix Rising was accused of making the comment just before half-time in their second-tier USL Championship game.
Loyal players returned after the break but walked off when the referee blew his whistle, forfeiting a match they were leading 3-1 and ending their chances of reaching the play-offs.
"They had my back and wanted to make a statement that we aren't going to stand for this hate in our game," said Martin, who is gay.
"This was not the first time I've heard this homophobic slur. However, it's the first time in my eight-year playing career that a slur has been directed at me during a game.
"The collective decision to walk off the field in solidarity and forfeit the match speaks volumes of their support for me.
"Ultimately I hope this can be another example that we have a long way to go in educating ourselves and kicking hate out of our game."
Phoenix Rising said Flemmings "vehemently denied" the allegations, and the player posted on Twitter that "the accusation was false", adding "my fellow team-mates will support my claim".
Loyal forfeited a match against LA Galaxy II last week after an alleged racial slur was aimed at midfielder Elijah Martin. The player accused of making the comment has since been let go by Galaxy.
Loyal players took a knee before walking off during Wednesday's second division game agaisn Rising.
Loyal manager and executive vice-president Landon Donovan, who played in the Premier League for Everton, said: "We went through a really hard incident last week in the LA match and we made a vow to ourselves, to our community, to our players, to the club, to USL, that we would not stand for bigotry, homophobic slurs, things that don't belong in our game."
Martin was sent off after the incident in the confusion but the red card was rescinded by the referee.
Instead, one was given to 38-year-old former forward Donovan - the United States' second-most capped player - after he came onto the pitch in the aftermath.
In a statement, the USL Championship said it was aware of the allegation and an investigation was under way.
"Foul and abusive language of any type has absolutely no place in our society and will not be tolerated in USL matches," it added.
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