On Wednesday afternoon in Melbourne, American teenager Madison Keys had the biggest win of her young career when she upset seven-time Grand Slam champion Venus Williams in the quarterfinals of the Australian Open.

On Thursday, she'll face the other Williams Sister -- Serena, that is -- in the semis. If she's freaked out by the success and paralyzed by the task ahead of her, she's doing a great job of hiding it.

In press after her win over Venus, Keys was asked how she had been enjoying her breakout tournament, which includes a win over the No. 4 seed, two-time Wimbledon champion Petra Kvitova, in the third round.

"Well, I've been eating Tim Tams," she said, referencing the Australian-made chocolate. "There's that."

Keys got into tennis when she was a young child and saw Venus playing tennis on the television. She wasn't drawn to Venus's game, though -- she was drawn to her dress. Keys realized that in order to wear a dress like Venus was wearing, she would have to pick up a tennis racket. And so she did.

The rest, as they say, is history.

When you watch Madison Keys play tennis well, it's hard to imagine her doing anything else. She looks like she was born to play the game. She's tall, trim and strong, and she moves around the court if not exactly with grace, certainly with precision. She has a mammoth serve, one that is both reliable and lethal, a difficult combination to find in the women's game. She never looks like she's wasting energy -- the outbursts are few and far between; there's not a trace of showmanship or dramatics. She's calm, collected, even-keeled. She looks sure of her next move, even if she's not. There's no panic in her game.

And those groundstrokes. Can we talk about those groundstrokes? At the French Open last year, the speed of groundstrokes were measured, and Keys' were faster than everyone else's, even on the men's side. When she dials in and aims for a target and gets her feet set in time, the ball comes off of her racket like it's being shot from a rifle. Her opponents are left mostly helpless on the other side of the net -- they can only pray that she missed the bullseye by an inch or two.

Seeing Keys dialed in is already one of the most breathtaking sights in tennis. And she's not even 20 years old yet.

People watching Keys for years have always known how special she is when she zones on the court. The problem was, it wasn't a sight seen too often. The power coming off of her racket was too much for her to handle, and so instead of a panic-free, sure-fire, precise display of power, it far too frequently became an uncontrollable disaster. Keys didn't trust herself and her game completely, and instead of letting her talent overpower her opponent, it overpowered her. Sure, there would be breathtaking moments where she was putting it all together, but then, in a seemingly unprovoked incident, it would be gone.

Now, at least at this Australian Open, the ratios have been inverted -- she loses herself and her game at times during the match, but she is also able to take a deep breath and reign in her power before the damage becomes irreversible.

A lot of this has to do with Keys maturing, gaining the experience on tour, and growing into her body and her talent. And a lot of it has to do with her new coach, three-time Slam winner Lindsay Davenport.

As reported by Christopher Clarey of The New York Times, last fall, after a year where Keys was full-time on the WTA tour and turned from 18 to 19 but only rose from No. 39 to No. 32 in the rankings, she went to her agent Max Eisenbud -- who she shares with superstars Maria Sharapova and Li Na -- and said that she was ready to stop working with the USTA and start developing her own team. Even Eisenbud didn't think that Keys would be ready to make such a move so soon, but he quickly accommodated her wishes and set her up to work with Davenport during the offseason.

Since Davenport is a mother of three young children and had no desire to be a full-time coach on the tour, this was thought to initially be only a temporary arrangement. But Davenport and Keys clicked instantly, and soon the former No. 1 and current Tennis Channel commentator was figuring out how to make it work. She saw the potential in Keys and in their partnership, and didn't want to miss out on something so helpful.

Clearly, the benefits have been immediate.

It makes since why Davenport and Keys work together so well. They both have a strike-first game that relies heavily on power and control, less on movement and touch. But more than that, they share a laid-back, friendly and measured temperament that is rare in a championship-caliber athlete. Sure, they both have an overwhelming desire to win and to be the best, but on the court, that impulse manifests itself more as ice than fire.

Before teaming with Davenport, Keys hadn't made it past the third round of any major. Now, she's one match away from the final, and has seemingly cemented herself as the Next Big Thing in American tennis.

If it seems like perhaps we've been here before, that's because we have. Two years ago at the Australian Open, a precocious American up-and-coming teenager had a breakthrough tournament, upset a Williams Sister in the quarters to make her first semi of a major, and was named the successor to the American tennis throne. That teen was Sloane Stephens, and that Williams Sister was a hobbled Serena. It was easy to get carried away with that moment -- after all, Sloane had all of the talent in the world and seemed ready for her close-up.

But the years since have been one disappointment after another for Stephens, who has yet to make it back to the semis of a Slam, still hasn't won a title, and often seems like she doesn't care about winning at all. In fact, last year in Charleston, Stephens said that she didn't think it would be a big deal if her ranking fell down to the 800s, and told me and other reporters, "I'm not rushing to try and do anything fabulous."

That's where Stephens and Keys seem to differ the most. While there is no panic in Keys' aspirations, there's no sign of contentment or complacency either.

"I mean, it definitely feels amazing," Keys said after her big win over Venus. "It's one of those things where you want to feel this way all the time. But it's not, you know, this unbelievable excitement either 'cause you want to keep winning and you want to keep doing better."

Keys is facing an unenviable task in her next match -- Serena Williams is a tough out at any point in any tournament, but when she makes it to the latter stages of Grand Slams she's particularly lethal. But unlike many of Serena's opponents, Keys can match her power. And, if Keys' matches against Kvitova and Venus are any indication, she won't be overwhelmed by the moment.

She might not be the Serena Williams successor that American tennis fans have been searching for, but she doesn't need to be. Keys has the game, the attitude, and the guidance to do something very special in her own right.