US Open: Defending champ Angelique Kerber upset by Naomi Osaka

Angelique Kerber of Germany returns a shot from Naomi Osaka of Japan during the first round of the U.S. Open tennis tournament Tuesday Aug. 29 2017 in New York

Osaka, who grew up in NY, broke for 5-3 and sealed the opening set with a sizzling victor down the line under the closed roof at Arthur Ashe Stadium. "So that helped me focus and concentrate, which I needed as Angelique gets everything back".

Osaka also converted four break points and won 63.2 percent of Kerber's second serves-again, a sign of her dominance.

The 31-year-old Spaniard recovered from 3-5 down in the opening set against the 85th-ranked Lajovic, who has never won a match in NY. "I just really want to play good here", said the World No. 45 Osaka after the match.

Kerber then took the same court where she beat Pliskova for the title previous year and took another stinging defeat in what has been a season-long slump since winning her second Grand Slam title.

Kerber struggled with her serves, committing her fourth and fifth double faults in the eighth game of the first set that allowed Osaka to clinch the first break of the match.

She carried her momentum into the second set by breaking Kerber in the first game.

The 36-year-old Swiss, who missed the 2016 US Open to rest a knee injury, takes on US teenager Frances Tiafoe under the lights, looking to take his first round record to 17-0.

One man certain to finish under the roof on Tuesday night was Roger Federer, whose capture of the Australian Open and Wimbledon titles in 2017 has taken his Slam count to 19.

In the day's other matches, Czech 23rd seed Barbora Strycova dispatched Misaki Doi 6-1 6-3, Yanina Wickmayer upset 28th-ranked Lesya Tsurenko 6-3 6-1, and Sorana Cirstea from Romania beat Lesley Kerkhove 6-1 6-3.

It was Osaka's first victory over a top-10 opponent after she was oh-so-close to beating a top player here a year ago, blowing a 5-1 lead in the third set and losing to Madison Keys in the third round.

She almost upended Keys in the U.S. Open's third round past year, leading 5-1 in the third set before losing in a tiebreaker, a collapse on her mind in the latter stages Tuesday. Osaka advanced to a second-round match against either Denisa Allertova of the Czech Republic or Rebecca Peterson of Sweden.

Heis bidding for a record sixth crown in NY.

The German sixth seed has failed to win any titles in 2017 and will drop out of the top 10 after suffering a 6-3 6-1 humbling at the hands of the Japanese-American youngster in just 65 minutes.