Serena had received a warning, a point penalty, and finally, a game penalty after an outburst that saw her call the umpire Carlos Ramos a thief.
Osaka and Williams were together after the match as Osaka was awarded the trophy for winning.
During a changeover, Williams resumed her argument with the umpire, this time saying he was attacking her character and was a "thief". "I have since texted her coach to make sure she understands that she is celebrated and how proud I am of her".
"I couldn't tell what was going on, it was so loud and a little bit stressful", Osaka said of the moment. He did what he had to do in that match, because she overcame the limit.
On the other side of the net, though, the 20-year-old Osaka kept her cool in her first Grand Slam final to win 6-2 6-4.
Williams received wide support in her claims after a series of code violations issued by umpire Carlos Ramos saw her attack the man in the chair as she lost the US Open final to Japan's Naomi Osaka in NY last weekend.
The Japanese player's breakthrough triumph in NY was overshadowed by an explosive row between her opponent Serena Williams and umpire Carlos Ramos.
Later this week, it was no longer only Williams and Ramos being criticized for their conduct, but also an Australian cartoonist for his depiction of the incident.
According to McEnroe, Ramos should not have given Williams a violation for breaking her racquet and should have warned her early on about what would happen if she did not move on.
"I know the way that I was brought up, people tell me I act kind of Japanese so I guess there is that".
One of the most controversial Grand Slam finals of all time divided tennis and triggered a debate about sexism in the sport, fuelled by Williams's assertion that Ramos would not have dealt with a male player in the same way.
A teary-eyed Osaka addressed the crowd, saying (via ESPN), "It was always my dream to play Serena in the U.S. Open finals".
While Williams was immediately backed by the Women's Tennis Association (WTA) and the United States Tennis Association (USTA) and hailed as a hero by countless feminists and the establishment media, Ramos kept quiet, as International Tennis Federation (ITF) rules bar umpires from commenting on their matches. And the judge at the heart of the controversy, chair umpire Carlos Ramos, has said only that he is "fine" and is in a "delicate position". "Do not worry about me!"