Junior Flemmings of Phoenix Rising has been banned for six matches for a homophobic insult aimed at San Diego Loyal's Collin Martin.
The Jamaican was found to have directed "foul and abusive language in the form of a homophobic slur" at Martin, who is the only openly gay player in football in the United States.
The incident in last Wednesday's USL Championship match prompted San Diego to walk off the pitch in protest. The referee had mistakenly sent Martin off, apparently thinking he was the abuser as he reported Flemmings' comments to the officials.
A heated discussion between head coach Landon Donovan, opposite number Rick Schantz and the referee followed. San Diego returned to the pitch after half-time but only to take a knee before walking off again.
Flemmings issued a statement on social media denying the abuse, but Rising placed him on administrative leave last Thursday while the league conducted an investigation into the incident.
The USL Championship is one tier below Major League Soccer in the United States.
On Tuesday, the league confirmed the punishment stating: "The USL Championship announced on Tuesday, following an investigation that included interviews with 11 individuals, including players, coaches and match officials, that it has issued a six-game suspension and undisclosed fine to Phoenix Rising FC's Junior Flemmings for the use of foul and abusive language in the form of a homophobic slur during the club's match against San Diego Loyal SC on September 30.
"Per the player's contract, Flemmings could also be subject to additional discipline from Phoenix Rising FC and remains on administrative leave.
"Flemmings' suspension covers the entirety of the 2020 USL Championship Playoffs."
Martin released a statement on social media in the aftermath of the incident thanking his team-mates for the solidarity shown in the walk-off and saying he hopes it will eventually help "kick hate out of our game."
"I truly want to focus on and that is the response of my coaches, team-mates, and the organisation," Martin said. "Their collective decision to walk off the field in solidarity and forfeit the match speaks volumes of their support for me and what this organisation is standing up to.
"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."
Head coach Donovan - whose playing career included stints at Bayern Munich and Everton - also explained after the incident that the Loyal declared they would say "I will act, I will speak" if any offensive comments were made toward the team's players.