NEW YORK — She sneaks up on you, doesn’t she?

Just ask Coco Gauff.

One minute, the American tennis world is gaga over Coco. The next, someone named Emma Navarro is sweeping her off Centre Court at Wimbledon. Just shy of a month later, she’s knocking her out of the U.S. Open on Arthur Ashe Stadium, the place that was supposed to be the defending champion’s living room for the next decade or so.

One minute, she’s all shy and soft-spoken, telling sweet stories about her 90-something grandmother sitting at home in Connecticut, watching and rewatching her matches before calling her with motivational advice. The next, Navarro is savaging Zheng Qinwen, the Olympic gold medalist and Australian Open finalist, doubling down on previous comments that Zheng doesn’t respect Navarro or the sport of tennis.

As Navarro, the 23-year-old former NCAA champion for the University of Virginia, has cruised up the rankings, the word “steady” has kept attaching itself to her. Something about the human backboard nature of her play, the hard, (but not too hard), flat power of ball after ball after ball opposing off her racket. The beauty of her game, her economic and elegant movement, and the subtle scything of her forehand almost go unnoticed.

She is plenty steady, sure, but that doesn’t begin to describe her. Stealthy is more like it.

Sixteen months ago, she was ranked No. 121 in the world. A year ago, she was No. 61. She spent last fall playing the tiniest WTA Tour events she could, even going to some ITF tournaments, one level below the WTA Tour. She won two of the tournaments she played and went deep in most, earning enough points to show up at the 2024 Australian Open as the No. 27 seed.

There was another benefit, too.

“I don’t know a single tennis player, recreationally, juniors, any level, that plays worse if they win a lot,” said Patrick Hieber in an interview. Hieber is a founder of LTP Tennis, the Charleston Academy where Navarro has trained since she was 14. He is also one of her coaches.

“Winning a lot is really good for you.”

For Navarro, it became something of a habit. She kicked off the year making the semifinals in Auckland, then won her first WTA Tour event in Hobart. Merely “steady” players don’t tend to do that, not at the top levels of the women’s game.

Steady players generally can’t pirouette out of the corners, or scramble back into a point with a flick, or slam passing shots that zip past opponents the calibre of Coco Gauff and scare the lines before they can turn their heads. As Maria Sakkari, a top-10 player, put it to Ben Shelton, her partner at an exhibition with Navarro in Indian Wells, Navarro is more stealth than safe.

“Yeah, Ben, she’s like low-key really good.”

Pretty much everyone knows how good she is now, including Navarro. When she was up a set but down 1-5 in the second set of her quarterfinal match against Paula Badosa Tuesday, Navarro could feel that she wasn’t going to have to work overtime.

She could get it done then and there.

“If I could push, make her think a little bit on her service game, maybe I could sneak my way back in,” she said.

“Sometimes you’re out on the court and you picture yourself playing a third set.

“When I was out there, I didn’t picture myself playing a third set.”

Push is the keyword there. For Navarro, born in New York but raised in Charleston, it’s learned behavior.

Steadiness was her default mode. It worked well with the other quality that those who know her best use to describe her, which is perfectionist. Both sound like good qualities for a professional tennis player.

Not so much.

Tennis tortures perfectionists. The best players lose nearly half of all the points they play. Win 53 percent and you might be the best in the world.

In the case of Navarro, who could do that human backboard impersonation from the time she was a small girl, the perfectionism drove her toward steadiness. At its most fundamental, tennis demands that players hit the ball over the net and into the court. Navarro could do that all day and damn it felt good.

That was the specimen that Peter Ayers, her coach at LTP, inherited when Navarro became his responsibility as a young teenager. She did so many things so well. Such a pure ball-striker. So much commitment, a desire to be the best tennis player she could possibly be. She was fast. She even liked gym sessions.

She hated to miss, though. That was a problem.

Emma Navarro’s runs at Wimbledon and the U.S. Open have catapulted her into the wider tennis world (Matthew Stockman / Getty Images)

A good problem because she didn’t miss very often, but the steadiness that allowed for that, and happiness that it brought, was a dangerous thing. Ayers knew it would only get her so far.

“We had to redefine mistakes. Not just the ball that’s wide or long or in the net, but, ‘Hey, when you hit that ball in the court right there, that was a mistake. A worse mistake than missing it six inches long. Here’s why,’” he said.

A good opponent would smash a lot of the balls Navarro was putting back.

“It’s a bigger mistake to let your opponent derive all the confidence that comes from getting to do that than taking a crack at it,” Ayers said.

That battle continues to this day, he said. The higher the level, the more you need to gamble on your control in the name of being aggressive.

Ayers, who is 51, has been around long enough to know that the key to coaching, especially an individual sport, is figuring out what’s best for each player and working with that rather than trying to enforce a strict approach.

Like a lot of top juniors, Navarro tried for a time to do high school online to allow her more flexibility for the training, practice and travel that junior tennis requires. She pretty much hated it. She was a social teenager who needed to lead a normalish life at a normal high school. If her tennis suffered, so be it.

It didn’t, though. She was willing to rise in the pre-dawn darkness to train before school started, then return to the courts after school for several more hours of practice.

“She wanted the brick-and-mortar experience,” Ayers said. “It was what she needed and what she wanted and we made it work.”

Emma Navarro beat Coco Gauff at both Wimbledon and the U.S. Open (Clive Brunskill / Getty Images)

As a coach, sometimes you just get lucky. What Navarro, who is 5ft 7in (170cm), may lack in size, she has made up for with her commitment to make herself the fittest, strongest athlete she can be. She has worked for years with a trainer named Brent Thacker and has the power and quickness to show from it.

She didn’t play other sports seriously growing up and lacked a natural understanding of how to battle an opponent. She was great in her space, at seeing the ball come over the net and putting it back. She was less great at looking across the net and figuring out the dynamic of the interaction between her and the player across the court.

Ayers and Thacker got creative. They taught her how to guard someone on a basketball court to respond to moves. She boxed and worked with a heavy bag. She learned to keep her head up and to read what was coming at her, which doesn’t always come naturally to tennis players whose opponents are roughly 80 feet away.

“You don’t feel how intense that interaction is,” Ayers explained. “How to be on time and more aware of the interaction you’re having with the person on the other side of the net.”

Next on the other side of the net is Aryna Sabalenka, the world No. 2 and the biggest hitter in the world, for a match that may feel like those boxing sessions Ayers and Thacker put Navarro through. Sabalenka can get wild though, which may also be a chance for that innate steadiness to help Navarro carry the day by stealth.

“Trying to scrap out some longer points,” she said. “Make them hit one more ball.”

(Top photo: Henry Nicholls / AFP via Getty Images)