The day before the biggest match of her young tennis career, 19-year-old Sloane Stephens made her way to a hot dog stand on the grounds of the Australian Open, holding a tennis ball with her named signed on it.

“Hey all! I’m hiding this ball on-site at the @AustralianOpen,” she tweeted, attaching a photo of her grinning along with the signed ball. “Find it & win 2 box tix 2 my match 2mrw. Clue to come.”

The future of American women’s tennis has a sense of humor like that: she is a magnet for the camera after matches, her wide grin lighting up the TV, her sarcasm and playfulness always present. But Wednesday afternoon in Melbourne (Tuesday night EST) she was all business in her first-ever Grand Slam quarterfinal at the Australian Open against Serena Williams, stunning the 15-time majors winner 3-6. 7-5, 6-4 in a colossally dramatic affair.

While Serena Williams battled injury from midway through the second set to the finish of the match, it was her compatriot, 12 years her junior, who held her nerve in the end, sending shock waves throughout the sporting world.

It is Serena that Sloane has been compared to over and over again. Sloane, a teenage African-American beauty with chiseled biceps and a solid game, expected to be the next big thing: the next Serena Williams.

It’s a question she gets a lot, along with one about her thoughts on being the “future” of tennis in the States. But Sloane isn’t Serena on court or off, and for tennis, that’s OK. The game is about to welcome a whole new personality: a bubbly one.

“Journalists just ask me that in press conferences when they’re not sure where to start,” Sloane says, addressing the Serena and future-of-tennis topics at once. “It always happens.”

But she hasn’t always been in the final eight of one of the biggest tournaments on circuit, and her test Wednesday was the ultimate one.

“It just happens to be Serena. She's obviously one of the greatest players to ever play the game,” Sloane admitted prior to the match. “Without all that, it's still a tennis match … The court's the same size. You're still playing a regular person across the net. You've just got to go out and play.”

Sloane has been on the radar of tennis fans for years now. The teenager has bounded up the rankings in 2013, registering a 9-2 record coming into Wednesday’s affair.

She’s done a photo shoot with Teen Vogue, chatted on CNN, been the focus of countless ESPNW pieces and is the face of the Under Armour brand in tennis (her clothing sponsor). Sloane’s arrival on the tennis scene has meant new hope for the American crop, which has lagged in producing a great new champion.

This Australian Open has marked the first major in the Open Era where no American male has a Grand Slam title to his name (following Andy Roddick’s retirement last year). And while Serena and Venus continue to be the beacon of the sport, no outright future champion has made his or her stamp.

Until Sloane, perhaps.

“She can be the greatest player,” Serena said earlier in the week in Melbourne.

Their backgrounds are drastically different: Serena, brought up with sister Venus in a tough neighborhood in Los Angeles, was a teen star by the age of 17, winning the U.S. Open in 1999 and becoming a global icon.

But Sloane is the daughter of a former college swimming mother and a NFL running back John Stephens, who passed away in 2009 when Sloane was just 16. Her tennis success has been more slow to come, but only because in the modern game of tennis, it takes a little more time.

While Williams plays a brutal game from the baseline that relies on sheer power, Stephens’s game is a bit more reliant on her crisp strokes being placed deep in the court, the construction of each point being steady and precise.

“I kind of just realize that this is how it works, this is what I have to do to be great,” Sloane said last week. “It's worked out so far.”

But whether or not she does become the next Serena, the next star of American women’s tennis, Sloane has been a welcome sight in the locker room—at least for Serena herself.

“I saw her in the locker room. She was another black girl,” Serena says, joking about the first time they met. “I was like, ‘Hey!’ That's when I first noticed her. ‘What up, girl?’ ”

For now, there is no Serena-esque entourage or a million Twitter followers or the kind of brutal force on the court like her predecessor. In fact, Sloane needed to turn to Twitter just to fill her player’s box.

“You get 16 tickets. I had one person,” Sloane explains, laughing about her contest. “I think we could manage to give a few away.”

Sloane next gets world No. 1 Victoria Azarenka in the Australian Open, the player who most recently challenged Serena on the tennis scene.

For now, the young American is soaking in her win over a player she once had a poster of on her bedroom wall.

"I guess I should hang a poster of myself now," she said on court after the match, with a beaming smile.