Ten. That’s both the number of years and number of titles between defending US Open champion Angelique Kerber and her first-round opponent, world No. 45 Naomi Osaka.

Two. That’s the amount of sets it took underdog Osaka to dethrone the crown-wearing Kerber in just over an hour on Tuesday at the 2017 US Open, 6-3, 6-1, under the roof in Arthur Ashe Stadium.

Osaka came out firing on all cylinders. The 19-year-old’s game was keen in all aspects, from a dependable serve, to a devastating backhand that had the young player ripping balls by Kerber. Overall, she secured 22 winners and won 86 percent of her net points in the pair’s first meeting.

Besides her elevated game, Osaka took the court with the composure and grace of a longtime player, stifling any disappointed outbursts or overtly boisterous celebrations. Her emotional resolve was a hard lesson learned a year earlier on the very same court. The then-18-year-old dissolved into tears after blowing a 5-1 lead to American Madison Keys, to whom she ultimately fell, 7-5, 4-6, 7-6, in their third-round battle at the 2016 US Open.

Her win on Tuesday marked her first victory against a Top 10 opponent in only her second main-draw showing at the US Open. And better yet, she backed it up on Thursday, fighting past Denisa Allertova, 6-3, 4-6, 7-5, and into the third round.

Could we be on the precipice of Osaka’s ascent into tennis domination? Or is it just a glimmer of greatness from a player still in the callow state of her career?

Osaka’s not a newcomer to squaring off against some of the biggest contenders in the game.

2014 was her first major victory, when she upended 2011 US Open champion Sam Stosur at the Bank of the West Classic in Stanford, Calif, 4-6, 7-5, 7-5. The then-16-year-old, who at the time was ranked No. 406, clocked serves averaging 120 mph and won after saving a match point.

That was when the Japanese native thought that maybe, just maybe, she had what it would take to tussle with the tennis elite.

“That match that I beat Stosur," Osaka replied to a reporter who asked when the young player started to gain confidence in her game, “I had, like, a little bit of thought of, hey, maybe I can play against these players, right?”

That slight, almost cautionary, self-confidence stayed with Osaka. 2016 began when she posted an impressive run at the Australian Open, making it through qualifying before falling to two-time Grand Slam champion Victoria Azarenka, 6-1, 6-1, in the third round.

Success followed her to the clay courts that year, when at Roland Garros, Osaka cruised past No. 32 seed Jelena Ostapenko, who would claim the French Open title a year later, in two sets, 6-4, 7-5. She went on to take No. 6 seed Simona Halep to three sets in the third round before finally falling, 4-6, 6-2, 6-3.

August 29, 2017 - Naomi Osaka in action against Angelique Kerber at the 2017 US Open. (USTA/Garrett Ellwood)
Photo by:  (USTA/Garrett Ellwood)

Osaka’s crucible came at Tokyo in 2016, when after knocking out Misaki Doi in the first round, she dropped only three games to No. 6 seed Dominka Cibulkova in Round 2, defeating the world No. 12, 6-2, 6-1. She went on to make a stirring run in Tokyo, advancing all the way to the final before losing to Caroline Wozniacki.

"After the match against Cibulkova,” Osaka said, “I think I started thinking I could possibly be a threat.”

2016 was Osaka’s first Top 40 year-end finish, and she was the recipient of the WTA Newcomer of the Year Award.

She started 2017 on a high, defeating longtime idol Venus Williams in Auckland before losing in the quarterfinals to No. 8 seed Ana Konjuh.

But the rest of the year has been less fruitful. Since her Auckland run, she has consistently seen early departures from events, unable to make it past the third round of any tournament.

Toronto seemed promising for the young Japanese player. She qualified into the main draw, reaching the third round and stealing a set from top seed Karolina Pliskova before having to retire due to an abdominal injury.

“Yeah, well, having to withdraw really hurt my feelings,” Osaka mentioned to the press at her post-match conference on Tuesday, “especially since I was playing the No. 1 and felt like I was doing really well.”

But her first-round send-off of Kerber could be the catalyst that Osaka has been preparing for.

She is one of just four teenagers in the world's Top 100, entering the US Open ranked No. 51. And even though she’s only appeared in six total Grand Slam main draws coming into the 2017 US Open, she has already reached the third round in all four majors.

If Osaka hopes to make it through the fortnight, she’ll have to keep the momentum and mindset going that she had in the Kerber match.

Her mental game is still developing, and her coach David Taylor, according to Osaka, has made it a priority for his player.

“He talks to me a lot about positivity because I tend to be really negative on myself and to the point where I don’t really know what I’m doing anymore,” she said.

Should she successfully stave off the abdominal injury that plagued her Rogers Cup run earlier this summer, Osaka very well could break her all-time best Slam showing. Her quarter of the draw, should her whipping ground strokes and level-headed demeanor stick with her, could result in a quarterfinal match against the opponent who thwarted her in the third round last year: Madison Keys.

But Osaka isn’t intimidated anymore – at least not after kicking out the defending Grand Slam winner in the first round.

“Moving forward," she said, "I feel like I know that I can play with the top players now, so I don’t have to be as nervous as I was today."