NEW YORK -- Aryna Sabalenka was still a teenager when she played her second Grand Slam main draw, in 2018 against Australian Ashleigh Barty -- in the crucible of the Australian Open.

Predictably, it did not go well. Sabalenka’s unfamiliar but all-too-audible grunts brought grunts, jeers and boos in return from the partisan crowd and, after winning a first-set tiebreaker, she fell 6-7(2), 6-4, 6-4. It was a wild match that foreshadowed a 4-4 career head-to-head between them -- and left Barty impressed.

“If Aryna really learns her game and her style and trusts that and backs herself,” Barty told her coach Craig Tyzzer afterward, “then there’s not going to be many people that can stop her.”

Barty, who would go onto the No.1 ranking and win three major titles, was only two years older than Sabalenka but seemed far wiser and emotionally centered. After that match a shattered Sabalenka thought to herself. “Oh my God, I think I will never get it.”

That was more than five-and-a-half years ago. As Barty and many in the game foretold, Sabalenka learned to trust her prodigious talent and, against the grain of her fiery personality, control those emotions. She won her first Grand Slam singles title, the Australian Open, back in January and next Monday, at the age of 25, she’ll become the 29th No.1 player in the 48-year history of Hologic WTA Tour rankings.

Sabalenka to claim World No.1 ranking after US Open

Iga Swiatek, following up one of the greatest seasons ever, after 75 consecutive weeks on top, will find herself No.2 after she lost a fourth-round match Sunday at the US Open to Jelena Ostapenko.

This was the third consecutive major that Sabalenka had a chance to catch Swiatek. Before Roland Garros began, Sabalenka was asked if she was ready to be No.1.

“I think yes,” she said, smiling. “I don’t know. Yes, I think so. I think I improved a lot, and I have everything to be No. 1. But I don’t want to focus on that. I just want to focus on my game, and I just want to bring my best game every time on the court, and after the season we'll see if I’m ready or not.”

This is her emerging voice of maturity. While Swiatek was disappearing from the field a year ago, Sabalenka was learning to reign herself in. After a well-documented struggle with double faults -- often more of a mental issue than physical -- Sabalenka self-corrected.

She played a magnificent championship match at the WTA Finals in Fort Worth but one lapse cost her against Caroline Garcia. Two of her three double faults came in the pivotal first-set tiebreaker.

“I just dropped my level for a little bit,” Sabalenka said later.

In the offseason, she made another important decision. While Swiatek is the only player with a full-time sports psychologist who travels as part of her team, a number of players employ part-time mental coaches. Sabalenka was one of them.

“To be honest, I decided to stop working with a psychologist,” Sabalenka revealed at the Australian Open. “I realized that nobody than me will help, you know? I spoke to my psychologist, saying, `Listen, I feel like I have to deal with that by myself, because every time hoping that someone will fix my problem, it’s not fixing my problem.’

“I just have to take this responsibility and deal with that. I’m my psychologist.”

Earlier in the tournament, Sabalenka said her goal was to be more “boring” to achieve better results.

“I was trying to scream less after some bad points or some errors,” she added. “I was just trying to hold myself, stay calm, just think about the next point.”

It worked. Sabalenka rolled through the field in Melbourne, defeating 2022 Wimbledon champion Elena Rybakina in the final. She was three months shy of her 25th birthday.

Champions Corner: How Aryna Sabalenka learned a new way to fight

Barty had just turned 23 when she won her first major, 2019 Roland Garros, and still 25 when she won her third before retiring. Swiatek was 19 as a first-time Grand Slam champion and celebrated her 22nd birthday at Roland Garros where she won her fourth major. Naomi Osaka won four Grand Slam singles titles by the time she turned 24. Ostapenko turned 20 during her title run at Roland Garros in 2017, Sofia Kenin was 21 when she won the 2020 Australian Open and Emma Raducanu won the 2021 US Open at the age of 18.

As it turned out, Sabalenka was a relatively late bloomer. This is consistent with her early career in tennis.

She was 15 before she played her first ITF events and never experienced the junior Grand Slams. Her first five tournaments, all in her hometown of Minsk, Belarus, resulted in five first-round losses over two years. She played her first WTA-level match in February 2017 after qualifying in Dubai but didn’t get her first victory until July, in the first round at Wimbledon. She finished that year at No.78, but the 2018 WTA Newcomer of the Year would vault into the top 20 a year later, after winning titles in New Haven and Wuhan.

Those in the game are hardly amazed she has risen to No.1.

“Because of the power she produces,” said Daria Kasatkina. “She’s one of the most powerful girls on tour. Plus, she’s moving very well. She’s very fit, and she’s always super hungry to win, and she’s a hard worker. So altogether makes crazy chemistry.

“To be honest, I’m not surprised. Especially after she won Australian Open, seems like some backpack fell off her shoulders, and you can see she’s playing now fearless. So, yeah, makes a difference.”

Sabalenka breaks through Swiatek's defense to win second Madrid title

Champions Corner: How previous losses to Swiatek helped motivate Sabalenka

Lindsay Davenport, a three-time major champion, captured the transformation on Tennis Channel during Sabalenka’s quarterfinal win over Elina Svitolina in Paris.

“The new-and-improved Sabalenka, the errors aren’t coming and Svitolina is going to have to win points on her own terms,” Davenport said. “This roll Sabalenka has been on the last three, four games -- there’s not much anyone can do, really.

“As an opponent, you could always say she can’t keep this up, she’ll start missing or get tired … all that’s changed now.”

And Barty, now enjoying the retired life back home in Australia, saw it coming.

“A lot of the time, our plans and our tactic against her was to just not give her the chance to work herself into a match,” Barty told CODE Sports in Australia. “She’s playing within herself and playing some really, really damaging tennis. You can see she’s a lot more calm and comfortable on the court, emotionally and physically.

“And she is causing some serious damage.”

Indeed, going into Monday’s Round of 16 match at the US Open, Sabalenka has won 20 of 22 matches at this year’s majors.

“I wish I would be like that few years ago,” she said. “Finally I understand what everyone was looking for and asking for. I need to be a little bit boring on court. I was trying to less screaming after some bad points or some errors. I was just, like, trying to hold myself, stay calm, just think about the next point.”

Next? After a long wait, Sabalenka will soon be the World No.1.