Williams was left hugely emotional as she repeatedly confronted umpire Carlos Ramos after he handed her a coaching violation before docking her a point and then a game in a dramatic second set.
The game penalty crucially put Osaka 5-3 up in second set and the 20-year-old kept her composure in incredibly impressive fashion to close out a historic win.
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After what was a massively controversial match, Osaka's brilliance should not be overlooked as she claimed Japan's first Grand Slam title.
The opening set was almost one-way traffic as the Japanese player controlled the rallies from the back of the court and appeared to show no nerves whatsoever.
Two breaks of serve ensured that she assumed the early advantage, but the opening set was the calm before the storm as Williams exploded.

Naomi Osaka celebrates winning the US Open

Image credit: Getty Images

The 36-year-old, who was targeting a record-equalling 24th Grand Slam singles title at Flushing Meadows, angrily confronted umpire Ramos after being told off for what he deemed a coaching intervention.
Ramos made it clear that he had spotted Williams' coach, Patrick Mouratoglou, making hand signals from the player's box.
Serena stormed up to his chair and informed him that she would never deliberately receive guidance from Mouratoglou, who was sat in the players' box.

Serena Williams's coach Patrick Mouratoglou

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She informed Ramos in strong terms:
I don't cheat to win! I'd rather lose... I'm just letting you know!
The confrontation came at a time when Williams perhaps needed a spark after she lost the opening set 6-2 to the dominant Japanese starlet, but she was never able to recover.
Williams was clearly still fuming as she sat at the changeover at 2-1 up in the second set, before getting a point docked for hurling her racket to the ground.
She then launched a series of verbal attacks on Ramos, demanding an apology for his call on the coaching violation to accusing him of being "a liar" and "a thief for stealing a point from me".
Ramos sent Williams into a further rage when he handed the 23-time Grand Slam champion a game penalty for the verbal abuse.

Serena Williams talks to the umpire during the US Open final

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In a further exchange, Williams again informed umpire Ramos that she is not a cheat and did not receive coaching from Mouratoglou, even adding that she had a daughter so would not do that.
You owe me an apology. I have NEVER cheated in my life. I have a daughter and I stand for what is right and I have NEVER cheated.

Serena Williams points at the umpire during her US Open final defeat against Naomi Osaka

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But Osaka was somehow able to keep her composure and she closed out the victory with Williams still unable to gather herself.

Serena Williams congratulates Naomi Osaka after the US Open final

Image credit: Getty Images

Despite the enormously controversial nature of the match, Osaka's stunning triumph must not be forgotten as she claimed Japan's maiden Grand Slam crown.
“I know everyone was cheering for her and I’m sorry it had to end like this,” said Osaka. "I just want to say thank you for watching the match.
“It was always my dream to play Serena in the US Open finals… I’m really grateful I was able to play with you."
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