Osaka: I didn't know what was happening

New York - US Open champion Naomi Osaka insisted she was mystified by Serena Williams' spectacular meltdown which saw the American legend accuse the chair umpire of being a "liar and a thief".

"I didn't know what was going on, I was just trying to focus. Since it was my first Grand Slam final, I did not want to get overwhelmed," said 20-year-old Osaka after her 6-2, 6-4 win.

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Williams was handed a code violation for coaching, a penalty point for racquet abuse and a game penalty for calling umpire Carlos Ramos a "liar and a thief" and insisting "you owe me an apology".

"Serena came to the bench and told me she had a point penalty and when she got the game penalty I didn't know that either," said Osaka, the first Japanese player to clinch a Grand Slam singles title.

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