As Naomi Osaka practiced at Arthur Ashe Stadium early Tuesday, her coach, Dave Taylor, dared her to whack a ball out of the 23,000-seat stadium.

She could not eject a ball, but the 45th-ranked Osaka would soon cast out the defending United States Open champion — and her own demons lingering at Ashe Stadium.

Osaka, 19, emphatically beat sixth-seeded Angelique Kerber, 6-3, 6-1, in 1 hour 5 minutes.

Kerber claimed her second Grand Slam title and the No. 1 ranking in New York last year, beating Karolina Pliskova in the final. Kerber’s ascent stalled this year, though, and she is plummeting. She has won no titles and is 0-9 against top-20 opponents. She also lost in the first round of the French Open, 6-2, 6-2, to Ekaterina Makarova.

The loss will drop Kerber out of the top 10 for the first time since 2015.

With Stan Wawrinka not defending his men’s singles title because of a season-ending knee injury, it is the first time that neither defending champion has reached the second round of the U.S. Open since 2003. That year, Serena Williams and Pete Sampras missed the tournament.