Column: The moments keep getting bigger for Kayla Day at the BNP Paribas Open

Kayla Day has boundless confidence, the fearlessness of youth and a powerful left-handed serve that she uses to move her opponents around the court. The 17-year-old from Santa Barbara, who turned professional in January, doesn’t seem to be missing anything from her tennis arsenal — except patience.

“I don’t think I’m that good at it,” she said. “I mean, I want my results to come, like, now. I want everything to be as fast as possible. I think my coach is really good about telling me, like, focus on the process and improving and the results will come.”

That’s already happening for Day, who became the youngest woman accepted into the main draw of the BNP Paribas Open when she was awarded a wild-card entry here.

Playing 35-year-old Mirjana Lucic-Baroni in a second-round match Friday at Stadium 2, Day held off a surge by the Australian Open semifinalist early in the third set to prevail, 6-4, 5-7, 7-5. Day won the last four games, breaking Lucic-Baroni twice before earning her biggest victory to date. She’s the youngest woman in the Women’s Tennis Assn.’s Top 200 — she started this tournament No. 175 — but she reacted Friday like a pressure-tested veteran who is accustomed to success.

“I just kept fighting and in the end it worked out,” Day said. “She was serving really well the entire match, and then I got down a break, 5-3, in the third and I just told myself to keep fighting and you never know what can happen, and in the end it worked out.”

Day, who will next face 2016 French Open champion and No. 7 seed Garbine Muguruza on Sunday, had been building up to this for a while but she has zoomed forward in the past year.

She reached the round of 16 in the junior competition at the 2016 French Open and the semifinals of the junior event at Wimbledon. After winning the U.S. Tennis Assn.’s girls 18s national title she got a spot in the main draw at the U.S. Open, where she advanced to the second round after her opponent, Madison Brengle, retired because of an injury. She lost in the second round to Madison Keys but then went on to win the U.S. Open junior title.

“It was such a good experience. I mean, I got two matches,” Day said. “I got to play one of the great American players right now, Madison Keys. It was such a great experience. And I got to play on such a big court, and that was the first time I had ever been on such a big court. I think that prepared me for today.”

So did her U.S. Open junior triumph. “Yeah, the junior run was really good, too,” she said, smiling. “I was really happy with the way that turned out. Yeah, I played really well that week.”

She had to turn down the prize money because she was an amateur then and was still considering college. “Then, after that, I won the wildcard into Australia and my parents were like, ‘OK,’” said Day, who lost her first-round match to Andrea Petkovic at this year’s Australian Open.

She said her adjustment to life as a pro has been smooth, largely because she traveled so much to play international tournaments at the junior level. Her life is unlike those of her friends back home, but she tries to keep in touch with them. She’s also forging new bonds, which isn’t always easy in this sport.

“It’s entirely different but I think they’re really happy for me,” she said of her old friends. “And I have a lot of tennis friends, which is good. I’ve traveled with the USTA a lot and there’s group of girls and I’m able to be good friends with them, which is kind of rare for the WTA when people don’t have a lot of friends.”

Where she goes from here is partly dependent on her patience and on her commitment to becoming stronger and fitter. “All the pros are in such good shape,” she said. “And when you go into a pro tournament, I think every match is really tough and really physical, as opposed to the juniors where, like, the first couple of matches you can…they’re normally a little bit easier.”

Day’s next opponent, Muguruza, said she knew little about Day and planned to watch videos to get an idea of what to expect. “I think I heard she won the U.S. Open Junior championship. Well, that’s a big thing, obviously,” Muguruza said.

Indeed, it is, but many other prodigies have won a title or two before flaming out. Day believes she’s equipped to avoid the pitfalls that can accompany success at a precocious age.

“I think I’m pretty grounded,” she said. “I like to stay really in the moment. I don’t like to think about what’s going to happen in the future or try and think about what happened in the past. Just focus on each day at a time because every day is tough.”

helene.elliott@latimes.com

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