The mother of United States midfielder Giovanni Reyna says she reported head coach Gregg Berhalter for kicking his wife when they were teenagers.
Danielle Reyna, wife of former US captain Claudio, says she reported the incident to US Soccer on 11 December.
She said it was "unfair" that "people were trashing" her son, 20, when Berhalter had done something "much worse" at a similar age.
Borussia Dortmund player Reyna did not start a match for the US during the World Cup in Qatar.
During a speech at a leadership summit in early December, Berhalter said an unnamed player was nearly sent home from Qatar for "not meeting expectations on and off the field".
Berhalter believed his comments would remain private but after they were erroneously permitted to be published, Reyna posted on Instagram that he was told by the coach that his role at the tournament would be "very limited" and that he let it affect his "training and behaviour".
He added that he had apologised to his team-mates and Berhalter.
Berhalter said he had been contacted during the World Cup by someone saying they were going to "take him down".
In a statement on Wednesday, Danielle Reyna, who won six caps for the US women's national team and was the roommate of Berhalter's now wife Rosalind, said she "did not make any threats" when reporting the incident from 1991 to US Soccer sporting director Earnie Stewart.
She said she contacted Stewart because she "was absolutely outraged and devastated that Gio had been put in such a terrible position" and that she felt "very personally betrayed" by someone her family "had considered a friend for decades".
She added: "I told Earnie that I thought it was especially unfair that Gio, who had apologised for acting immaturely about his playing time, was still being dragged through the mud when Gregg had asked for and received forgiveness for doing something so much worse at the same age."
She also alleged that Berhalter's statement, which was co-signed by Rosalind, "significantly minimised the abuse on the night in question".
She added: "Rosalind Berhalter was my roommate, teammate and best friend, and I supported her through the trauma that followed.
"It took a long time for me to forgive and accept Gregg afterward, but I worked hard to give him grace, and ultimately made both of them and their kids a huge part of my family's life.
"I would have wanted and expected him to give the same grace to Gio. This is why the current situation is so very hurtful and hard."
In Berhalter's statement he said he kicked Rosalind in the legs during a "heated argument" after they had been out drinking.
He said Rosalind "wanted nothing to do" with him immediately after the incident but they met seven months later to rebuild their relationship.
They have been together since and celebrated their 25th wedding anniversary over the New Year weekend.
Danielle Reyna said she hoped reporting the incident to Stewart would help stop attacks on her son.
She said: "At the time I called Earnie, many people were trashing Gio on social media due to Gregg's comments, and I didn't know when or if this would stop.
"I just wanted Earnie to help make sure that there would be no further unwarranted attacks on my son.
"I thought our conversation would remain in confidence, and it didn't occur to me at the time that anything I said could lead to an investigation."
She added that she now understands Stewart "had an obligation to investigate" but that she "did not ask for Gregg to be fired" and "did not make any threats" nor does she "know anything about any blackmail attempts".
In a subsequent statement, Claudio Reyna, who played with Berhalter on youth and high school teams as well as the US national squad, said he supported his wife and her statement.
He added: "I too was upset by Gregg's comments about Gio after the US was out of the World Cup, and I also appealed to Earnie Stewart on December 11 asking him to prevent any additional comments.
"While in Qatar, I shared my frustrations about my son's World Cup experience with a number of close friends, Earnie and Brian McBride among them. However, at no time did I ever threaten anyone, nor would I ever do so."
Berhalter's contract expired on 31 December and his position is under evaluation.
US Soccer said assistant coach Anthony Hudson will take charge of a training camp in January.