US Open defending champion Naomi Osaka and 15-year-old Coco Gauff talk about training together in years gone by and the friendship that their fathers have. (1:27)

NEW YORK -- Cori "Coco" Gauff stood in the center of Louis Armstrong Stadium as a near-capacity crowd of 14,000 looked on in adoration. The 15-year-old had just won an epic three-set thriller over Timea Babos in the second round, and now ESPN's Tom Rinaldi was asking her about her next match.

"A lot of people had circled on the draw who your next opponent is: the defending champion Naomi Osaka."

Before Gauff had a chance to answer, the crowd began to boo. Brief but loud, the jeers left little doubt who they would be rooting for on Saturday.

The teenager giggled nervously. "What's the question?" she asked as she glanced around.

"What are your early thoughts on that matchup?"

"I don't have any thoughts on it right now because I have to play doubles tomorrow with Caty [McNally] and I'm really focused on that," she said diplomatically. "I don't even know what today is. What's today? Thursday? So Saturday I'm going to think about the match."

Gauff may say she won't be thinking about the match, but that certainly won't stop everyone else in tennis from talking about it incessantly. It's a tantalizing narrative: The teenage wunderkind takes on the slightly-older wunderkind who herself played giant slayer just last year on the same court where they likely will play.

Since her incredible run at Wimbledon in July, Gauff has captivated even the most casual of tennis fans with her fearless play and joyful energy. At the US Open, she has become the youngest woman to reach the Round of 32 since Anna Kournikova in 1996, and the youngest American woman since Jennifer Capriati in 1991. And Gauff looks to keep her magical summer going and make history in Queens.

But it will take more than poise or athleticism to beat Osaka, 21, on Saturday. No woman in the Open era has ever defeated a player who was both the No. 1 seed and defending champion in their debut at a given major in 67 attempts.

The two have never played each other, but have known each other for several years and hit together once two years ago before the Miami Open. Their fathers are friends and talk regularly. The respect between the players seems genuine, and they are eager to see how they compare on the court.

play 1:51 Gauff's parents know Coco can be among the best of all time Coco Gauff's parents Corey and Candi join First Take to discuss how high their expectations are for their daughter.

"Obviously she's an amazing player," Gauff said of Osaka during her postmatch news conference. "We're both pretty young, but I'm a little bit newer to the game. So I'm just curious to see how my game matches up against her. Obviously I want to win."

"She's super sweet and I would love to play her, of course," Osaka said on Thursday, before Gauff had secured her spot. "When I hear people talking about someone, I want the opportunity to play them just to assess it for myself. You know what I mean?"

She'll get her wish, but she probably wasn't expecting animosity from the crowd. Then again, she probably wasn't expecting that last year either. For Osaka, hearing boos at Arthur Ashe Stadium, where the matchup will presumably be played on Saturday, will be nothing new.

During her first Grand Slam final during the 2018 US Open, she beat her longtime hero Serena Williams in one of the most controversial matches in tournament history. Williams was playing in her second major final since returning from childbirth and looking for her record-tying 24th Grand Slam title. The crowd very much wanted to see her do just that, and instead watched her receive three questionable code violations. By the time the match was over and Osaka emerged victorious in straight sets, the crowd was confused and angry, and made their displeasure known. Osaka hoisted the trophy in tears.

This year was supposed to be different. Over the past 12 months, Osaka won another major title at the Australian Open, took over World No. 1 and became one of the most recognizable and marketable tennis players in the world, a player who represents Japan but is equally beloved in the United States. She currently lives in Florida, like Gauff, but spent most of her childhood in New York. In some ways, she's even more of a hometown hero than Gauff. But now it seems she'll find herself as the villain once again on the sport's biggest stage.

Will that stop Osaka from beating Gauff? Probably not. Either way, Saturday promises to be the spectacle we've all been waiting for. Two of tennis' brightest young stars will be on show, foreshadowing a rivalry that could easily dominate the decade to come.