NEW YORK, NY, USA - The last time Naomi Osaka played on Arthur Ashe Stadium, the teenager dissolved into tears as her a commanding 5-1 final set lead over Madison Keys dissipated. One year on, she laid the ghost of that loss to rest, scoring a momentous 6-3, 6-1 upset of No.6 seed Angelique Kerber and the first Top 10 win of her career.

It was a brutal display of power tennis from Osaka, who struck 22 winners and took just 65 minutes to complete the upset - but there had been question marks over her fitness coming into Flushing Meadows. The World No.45 had retired from her last match in the third round of Toronto with an abdominal injury - still, she had served notice of her form even then by taking World No.1 Karolina Pliskova to a deciding set. Today, in a tight opening sequence of six consecutive service holds, the first indication of Osaka's peak came when the Japanese player fended off the first break point she saved with a long rally that she finished with a brilliant backhand winner.

No US Open defending champion had lost in the first round the following year since Svetlana Kuznetsova in 2005, but Kerber's service woes deepened in the eighth game of the set, offering up her fourth and fifth double faults en route to suffering the first break of the match. But it was in the following game that Osaka began to play some special tennis.

As Kerber counterpunched her way to two break points, memories of last year's collapse might have haunted her - but this year, the 19-year-old produced first a booming backhand winner and then a spectacular forehand pass down the line at full stretch to save both. Two points later, the German had netted a return and Osaka was a set away from her first Top 10 victory in 10 attempts.

Osaka's level kept on rising: the second set was a stunning display of power tennis as she broke Kerber to 15 in the first game and rode the momentum without letting up. Huge hitting saved a break-back point in the next game, and thereafter Osaka would break the former World No.1 twice en route to setting up a second round against either Rebecca Peterson or Denisa Allertova.

It wasn't just a milestone win for Osaka: today's match also marked the highest-ranked scalp for a Japanese player since Akiko Morigami upset World No.3 Nadia Petrova at Roland Garros in 2006. For Kerber, the loss will mean that exactly one year after ascending to No.1 for the first time, the German will fall out of the Top 10 after the US Open.