Japanese teenager Naomi Osaka has registered the greatest victory of her career by defeating defending US Open champion Angelique Kerber.

Osaka showed no fear and cruised to a straight-sets victory in the first round. 

The youngster says she had all the emotions going on under a calm appearance.

"when I actually won, I didn't do anything. So I was kind of sad about that. Especially since like when you're little you dream about playing on Arthur Ashe against a great champion. And then everyone asks me like why I don't show emotion, but I really want to, but I can't, you know. But yes, it's really special for me. Especially like, I think every first round grand slam match is special."

She received a nod from Kerber who tried to fight back.

"I was always believing until the end that I can turn around the match, because I turn around a lot of matches but she played good, especially also at the end of the match. I'm always trying to go for it when I have the chance. Today, I mean, she just went for it. I think she took the chances and she played a very good match. But for me it was for sure not the best day and not the best match."

Top seed Karolina Pliskova eased into the second round with a comfortable straight-sets win over Magda Linette.

And China's Peng Shuai, Zheng Saisai and Duan Yingying all made it through the opening round.

Peng reached the second round in straight sets at the expense of Amandine Hesse. 

Peng is taking nothing for granted against her next opponent Donna Vekic.

"The fact that I'm higher ranked than her guarantees nothing. I still have to give it my best. I hope that I am not as nervous as today, although it is normal to be nervous ahead of a match. But as all other players, I also hope I can play better tennis at a Grand slam like the US Open."

Men's action saw Rafael Nadal sailing past Dusan Lajovic in straight sets.

John Isner, Alexander Averev and Dominic Thiem all went through.