NEW YORK—On the same day Serena Williams lost her grip on the No. 1 spot, an American 18 years younger than her ascended to the top of the junior rankings. Last week, Kayla Day became the first American girl to win a junior Grand Slam since Samantha Crawford at the 2012 U.S. Open, snapping a 15-major streak of non-American champions.

Other than being a lefty, the most telling quality that sets Day apart from the other countless juniors vying for future greatness is her confidence. You can even see it in the way she walks—be it on court, around the grounds or in the pressroom.

The Santa Barbara resident captured her first major title in dominating fashion, defeating Viktoria Kuzmova, 6-3, 6-2, in the final. The 16-year-old had to rely heavily on her confidence and mental game to keep herself together. Partnered with Caroline Dolehide, she had suffered an emotional defeat the night before in the doubles final, double faulting on match point in a 13-11 deciding tiebreaker loss to fellow Americans Jada Hart and Ena Shibahara.


A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

But Day managed to put that tearful night behind her the very next day when she returned to the court.

“I think I was really able to mentally set aside what had happened and just move on,” Day said, “because I knew I had a really important match.”

Managing her emotions was crucial to her success over the three weeks in New York, because the teen also had to separate her pro U.S. Open experience from her junior one.

“I think, mentally, it was a little bit hard, just because it's such a long time being here,” Day said after the final. “I have been here for, I think, over three weeks. But my coach told me I needed to separate the two tournaments, to really make sure when I come back to play juniors, I'm coming to play a new tournament.”

Day won the USTA Girls’ 18s National Championship to earn a wild card into the women’s main draw. She faced Madison Brengle in the first round, and benefited from a retirement while leading 6-2, 4-2. The lefty then lost to world No. 9 Madison Keys, 6-1, 6-1.

“Yeah, I definitely think we'll see her around,” Keys said. “I think she has a great serve and a really solid forehand. No doubt that she'll be around.”

Though the scoreline was one-sided, the experience was unforgettable for Day.

“I think my favorite part was playing against Keys on Louie [Armstrong Stadium], a night match at the U.S. Open,” Day said just a few days before winning the junior title. “I feel like I gained confidence off it. I got to know the courts even better. More matches and competition beforehand helped me to come into the juniors.”


A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

Day doesn’t lack in support, either, as she gets set to make some big decisions in her career. Her coach, Henner Nehles, is a German-born former UNLV star who has worked with both Jelena Jankovic and Sam Querrey. He’s since begun working for the USTA, and currently trains a handful of 16-year-old girls.

“We always try to help the top prospects in that age group,” Nehles said. “And Kayla, right now, is doing quite well.”

Quite well is an understatement. Day turns 17 later this month, and she’s already ranked No. 269 on the WTA tour.

But Nehles has far loftier expectations for his student.

“It’s really hard to predict the future,” he said. “I think she can achieve great things. At the beginning of the year I thought she was going to be, for sure, [a] Top 100, Top 75 player [one day]. Now, six, seven months later, I can see her being a Top 30 player down the road.”

Day has proven that she has the game to reach the top of the junior world, and the mentality to do well in the big leagues. Nehles did not hesitate when asked what her greatest strength is.

“Confidence,” Nehles said. “Her confidence is very high. She understands her game. She knows what she’s good at and what she needs to do. That’s it.”


A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

A Brand New Day: U.S. Open junior champ Kayla Day is as confident as she is talented

Day already had some WTA experience coming into the U.S. Open, including two qualifying victories against Top 100 opponents in New Haven. Earlier this summer, she reached the final of an International Tennis Federation Pro Circuit $25,000 tournament, beating fellow high school senior CiCi Bellis along the way.

Bellis committed early to Stanford University—she unexpectedly announced on Tuesday that she's turning pro instead—but Day is taking her time with her decision.

“It’s not [about] a certain [pro] ranking,” Day said. “I think it’s whether I feel confident and comfortable enough to make that decision to turn pro. I just want to be confident that I make the right decision when I do.”

There’s that word again. Confidence has been key to Day’s recent success, and it will naturally be crucial for her future.

“College is a good option, in general,” Nehles said. “For Kayla, it depends on her. It’s a big decision to make. If she goes to college, fine. If she doesn’t go to college, fine. As long as she stands up for her decision and she owns it, either is good.”

For now, though, Day is focused on what’s directly in front of her.

“I think I’ll play more pros,” Day said, “and mainly [ITF] Pro Circuits in the U.S., stuff to build up my ranking. I’d like to [qualify] next year at the Grand Slams, and maybe I’ll play a couple juniors because I can’t play a full schedule yet.”

No matter what path she ends up taking, Day has a second strength to fall back on.

“She loves tennis,” Nehles said. “That’s a very good quality to have.”