A tearful Williams chalked the penalty up to being targeted for her gender during a discussion with U.S. Open officials. Williams told Ramos that her coach, Patrick Mouratoglou, gave her a thumbs-up, which is just a C'mon.
The 36-year-old, who was targeting a record-equalling 24th Grand Slam singles title at Flushing Meadows, angrily confronted umpire Carlos Ramos after being told off for what he deemed a coaching intervention. "Even when I was a little kid, I always dreamt that I would play Serena in a final of a Grand Slam", Osaka said.
Serena confronted the chair judge after receiving a coaching violation early in the second set Saturday. telling him she doesn't cheat to win. She previously insisted that she didn't receive any coaching and said she wasn't sure if the umpire played any part in deciding the match's outcome. "I'd rather lose. I'm just letting you know!"
The headlines were supposed to be about the American's bid for a record-equalling 24th grand slam title and Osaka trying to become Japan's first slam victor but instead an argument with umpire Carlos Ramos that escalated dominated the match.
Briefly, Williams appeared to be working her way back into the match, breaking Osaka for the only time to go up 3-1 in the second set.
Williams called Ramos a "thief" for stealing a point away and was hit with a third violation, this time for verbal abuse.
Playing on tennis's biggest stage in her first Grand Slam final, the enormity of the moment did not faze Osaka while Williams, contesting her 31st major final, looked unsteady. She unwrapped a new racket and then took the court to argue again some more about coaching. Williams said. "You owe me an apology".
Osaka, almost three years younger than her opponent, had never been beyond the fourth round at a slam prior to this week but, bar a very close match against fellow 20-year-old Aryna Sabalenka, has steamrollered through the draw.
"Then when I sat down, I said it again".
Hughes will chair Sunday's match between Novak Djokovic and Juan Martin del Potro.
He added the 2018 U.S. Open title to nine Australian Open and seven French Open tournament victories, as well as two Paralympic gold medals.
For Williams, this latest incident recalled a 2009 problem, when she threatened to shove a ball down the throat of a lines woman who called a foot fault.
Osaka holds dual Japan-U.S. citizenship.
The 32-year-old Murray, brother of former Wimbledon and U.S. Open champion Andy Murray, played with Mattek-Sands for the first time in the tournament.
Murray and Mattek-Sands received $155,000 for winning the championship.
Williams suffered life-threatening complications after the birth on September 1 of a year ago, requiring four surgeries to deal with blood clots.
The 36-year-old is back in the final in NY for the first time in four years and one step away, as she was at Wimbledon, from equalling Margaret Court's all-time record for slam singles titles.
With a seventh US Open title to go with those she won in 1999, 2002, 2008, 2012, 2013 and 2014 she can break out of a tie with Chris Evert for the most ever.