U.S. Open: Defending champion Kerber shown the door in Rd 1

Defending champion Angelique Kerber of Germany was knocked out of the U.S. Open in the first round when she lost 6-3, 6-1 to Japanese teenager Naomi Osaka on Tuesday.

Japan’s Naomi Osaka reacts after winning a point against Germany’s Angelique Kerber.

Japanese teenager Naomi Osaka sent defending champion Angelique Kerber crashing out of the U.S. Open first round on Tuesday, bringing a rare bright spot to a rain-lashed day at Flushing Meadows.

As players ran for cover off the outside courts, Osaka's big-hitting game and love of the big occasion thrived under the roof of the Arthur Ashe Stadium court.

The World No. 46, born in Japan to a Haitian father and Japanese mother, won 6-3, 6-1 as sixth seed Kerber became the first U.S. Open women's defending champion to lose in the first round since Svetlana Kuznetsova in 2005.

Osaka, who surrendered a 5-1 third set lead on the same court in losing to Madison Keys 12 months ago, fired 22 winners as Kerber went tumbling out of the world's top 10 as well as the tournament.

"At 4-1, I was hoping I don't do what I did last year," said the 19-year-old Osaka, who admitted suffering a brief flashback to her tearful loss to Keys.

"So that helped me focus and concentrate, which I needed as Angelique gets everything back."

Osaka will face either Sweden's Rebecca Peterson or Denisa Allertova of the Czech Republic for a place in the last 32.

"I just want to play good. I did that today and so I want to carry that into the next match," added the Japanese teenager, who secured her first career win over a top-10 player.

Kerber is the third top seed to go out in the first round after number two Simona Halep and seventh-seeded Johanna Konta lost on Monday.

Karolina Pliskova of the Czech Republic reacts after defeating Magda Linette of Poland.

Meanwhile, World No. 1 Karolina Pliskova eased into the second round with a no-nonsense 6-2 6-1 victory over Poland's Magda Linette as rain began to fall at Flushing Meadows on Tuesday.

The Czech, who will next face Paraguay's Veronica Cepede Royg or American qualifier Nicole Gibbs, outclassed her 72nd-ranked opponent after the roof on Arthur Ashe was closed just before the second set.

Pliskova, who reached the final here last year, broke twice in the opening set to take a commanding lead with a fine backhand passing shot as Linette struggled on serve.

After fighting off six break points in the fifth game of the second set, Pliskova rolled on to prevail on her first match point with a second-serve ace.

"I felt a little bit nervous walking on this court, especially after last year and the memories I have here," said Pliskova.