The 6-2 6-4 victory appeared routine enough but the one hour and 19 minute match will be long remembered for a row between Williams and the chair umpire.
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 winner, but instead an argument with umpire Carlos Ramos dominated the match.
Williams was furious when she was given a coaching violation early in the second set after a hand gesture from her coach Patrick Mouratoglou.
She was then docked a point for a second violation when she smashed her racquet after dropping serve at 3-3.
“I don’t cheat to win, I’d rather lose,” Williams told Ramos.
“I didn’t get coaching. You owe me an apology. I have never cheated in my life.”
???????????? This is so hard to watch
— Kimberley A. Martin (@ByKimberleyA) September 8, 2018
I have never seen anything like this in my life #USOpen18
— Maggie Gray (@MaggieGray) September 8, 2018