After more than three hours of battling in the hot Australian summer sun, relentlessly chasing down ball after ball to scrape her way out of an early deficit, Coco Gauff walked back into the center of the court at Rod Laver Arena.

As the crowd stood in ovation, a playful smile crossed the 19-year-old's face, and she jokingly danced, rocking her hips back and forth.

There had been few moments of levity during Tuesday's tense 7-6 (6), 6-7 (5), 6-2 quarterfinal match against Marta Kostyuk, and the relief was palpable in Gauff's moment of celebration.

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After she won the 2023 US Open, this tournament marks Gauff's first major as a Slam champion. While the attention has followed her since she first burst on the scene as a 15-year-old in 2019, she arrived in Melbourne fresh off yet another title in Auckland and as a favorite -- with all of the hype and expectations that come with such a distinction.

But while many of the other top seeds, including No. 1 Iga Swiatek and No. 3 Elena Rybakina, fell early, Gauff looked virtually immune to succumbing to the pressure. She didn't drop a set in her first four matches and even recorded two bagel sets. She further cemented her status as a leading contender with each passing round.

Kostyuk was Gauff's first true test. Kostyuk jumped out to a commanding 5-1 lead, and it looked as if Gauff would also be heading home. But she turned it around, winning the next five games, and ultimately, after a roller-coaster, error-laden afternoon, Gauff advanced to the Australian Open semifinals for the first time in her career. She also became the first female teenager to advance to back-to-back major semifinals since 2007.

Gauff hadn't been thinking about records or history during the match -- she simply had wanted to win and had done everything she could to do it.

"It was a fight," Gauff later told reporters. "I think today was definitely a C-game, so [I] didn't play my best tennis, but [I'm] really proud that I was able to get through today's match. Hopefully got the bad match out of the way and I can play even better."

No longer the emerging teenager brimming with potential, Gauff is now the one to beat.

And she is just two victories away from her second major title.

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Standing in her way of the final is her fiercest opponent yet: reigning champion Aryna Sabalenka. The 25-year-old and current world No. 2 won her long-awaited first major last year in Melbourne and had a chance to earn her second at the US Open before losing to Gauff in the final 2-6, 6-3, 6-2.

Sabalenka hasn't forgotten the bitter disappointment she felt after the loss.

After advancing to the semifinals with a win over Barbora Krejcikova on Tuesday, Sabalenka couldn't hide how excited she was to have the chance to avenge her three-set loss in New York.

"I love it," Sabalenka said. "After [the] US Open, I really wanted that revenge, and, I mean, that's a great match. It's always great battles against Coco, with really great fights. I'm happy to play her, and I'm super-excited to play that semifinal match."

The two have played six times. Gauff has won four of those meetings, but they split their 2023 matches, with each winning once. Sabalenka defeated Gauff in the quarterfinals at Indian Wells 6-4, 6-0, in March.

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Sabalenka returned to Australia with the singular goal of defending her title. She opened the season by reaching the final in Brisbane and has been all but unstoppable in Melbourne. In her first five matches, which included wins over two seeded players, Sabalenka has not dropped a set and lost a combined total of just 16 games. She won her third-round match over Lesia Tsurenko, the No. 28 seed, with a double bagel score (6-0, 6-0).

"Obviously Aryna, always a tough match with her," Gauff said Tuesday before she knew if she would be facing Sabalenka or Krejcikova. "I think she's playing well this tournament."

While Sabalenka has been nearly flawless throughout, Gauff showed signs of vulnerability on Tuesday. She had 51 unforced errors, nine double faults and just 17 winners. Kostyuk had success in her persistent attack of Gauff's forehand, a known liability, particularly in the second set. But despite her struggles, Gauff still dug deep and found a way to win, relying on what was working.

"I think she's an incredible mover, so it's like you really need to work for every point to win it," Kostyuk said. "I mean, backhand obviously is her strength. I mean, it's good. It's really good. She's not missing much from the backhand."

Alongside her coach Brad Gilbert, with whom she's worked since July, Gauff has actively tried to find ways to improve her game. Over the preseason, she spent two days working with Andy Roddick, the 2003 US Open champion who also was coached by Gilbert, in Charlotte, North Carolina, working on her service motion.

"[Roddick] is one of the best servers ever, so when he offered his advice, I flew to his home and we made some magic," Gauff said in an interview with Eurosport. "It was only two days there, but I think it was the most meaningful two days of practice that I've ever had."

Life has undoubtedly changed in some ways for Gauff since adding "US Open champion" to her résumé, but she is largely still the grounded and gregarious teenager the world first fell in love with 4½ years ago. Many of the routines she established early in her career remain and provide a familiar comfort, no matter the tournament or weight of the moment.

Her parents still travel with her and are both in Melbourne. While no longer her coach, and unable to sit in her player box since the US Open due to a combination of nerves and superstition, Coco's dad, Corey, remains an important member of her team and can often be seen in various locations around the stadium. Her mom, Candi, remains a visible and vocal stalwart in her player box and she even went viral for catching an errant ball Tuesday. (Gauff later downplayed her mom's big moment: "It wasn't that hard of a ball to catch.") The trio have been playing cards every night at their hotel.

Her younger brothers, Cody and Cameron, remain at home in Florida, but Gauff has routinely shouted out their athletic accomplishments during her interviews and publicly called out their lack of responses to her text messages. Both of their names appear on her sneakers, alongside the coordinates of the public park where she first began to play the sport and a quote her dad has told her since childhood: "You can change the world with your racket."

After her fourth-round match, she said the messages were a source of inspiration during tough times on the court.

"Sometimes when my mom thinks I'm negative when I look down, [but] I'm just looking at my shoe," Gauff said. "[It's] just a reminder that life is much more than tennis, [and] how I do on the court does not define me as a person."

Gauff has been talking about her Jaden Smith fandom since some of her very first press conferences, and while she's since starred in a New Balance commercial with him, that hasn't changed either. She told reporters last week she listens to Smith's song "Icon" before every match.

Despite being one of the most recognizable and well-known players on tour these days, Gauff has been able to stay somewhat under the radar around Melbourne -- something that doesn't happen in New York -- and she said that has helped her as well. She went to the movies during the first week to see "Poor Things," and was hoping to go back to see "The Iron Claw."

"I like the chill vibes here. I feel less stress here," Gauff said. "Just walking around in Melbourne, I don't really get recognized that much, which is nice. Just walking to dinner, you know, maybe one or two people notice, and it's something that I appreciate a lot."

While every match at the US Open became a must-watch event for American television audiences, the 16-hour time difference from the East Coast has lessened the glare. But it hasn't changed Gauff's focus.

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Thursday's women's semifinal matches at the Australian Open are a study of contrasts. Gauff versus Sabalenka is a blockbuster match featuring two major champions in a repeat of the US Open final. The second match features two first-time semifinalists in qualifier Dayana Yastremska and Zheng Qinwen, neither of whom was considered anywhere near the favorites at the start of the tournament. Yastremska had 200-1 odds according to ESPN BET.

Whether it is Gauff or Sabalenka, the winner will undoubtedly be expected to emerge victorious in Saturday's final.

But that expectation wouldn't change anything for Gauff if she were to advance.

"I don't really approach matches differently [since winning the US Open]," Gauff said Tuesday. "But there is definitely a change in just the energy. I mean, you do feel like you're the one to beat ... I think there's a quote, 'It's not easy to get to the top, but easier to get to the top [and] harder to stay there.' The goal is to stay here as long as possible and keep going upwards. I mean, I'm not at the top, but I'm up there."