Serena Williams on Day Three of the 2015 US Open on September 2, 2015 in Queens, New York. (Photo by Elsa/Getty Images)

There's a new Gatorade commercial out starring a young Serena Williams, and it begins with a question from an interviewer: "If you were a tennis player, who would you want to be like?" After a montage of her career highs and lows, the interviewer repeats the question, and Williams answers: "I'd like other people to be like me."

That kind of preternatural self-assurance has followed Williams over the course of her career, as she's racked up 21 Grand Slam tournament titles, four Olympic gold medals and several No. 1 rankings—the most recent of which has Williams with as wide of a gap between the top and the next-ranked player as at any point in history.

Now, she'll have to put her fiery self-assurance to work to manage what is, by any standard, an extraordinary test: winning the first single-season Grand Slam—in which a player wins all four major tennis championships in a calendar year—since Steffi Graff did it in 1988.

Plenty of people seem to think she'll do it. Tickets to the women's final match, in which Williams could reach this milestone, sold out before the men's for the first time in U.S. Open history. Media coverage is breathlessly saying a championship in Flushing Meadows could "cement Serena Williams as one of the greatest American athletes." Reporters are asking her if she now believes she's the greatest player ever.

[How women's tennis fought for equal pay]

Williams' responses to how she's confronting what lies ahead are exactly what you'd expect from a professional athlete, or any successful leader facing extraordinary pressure to reach a rare and seemingly out-of-reach goal. She's keeping the focus on the game. Not thinking too much about the numbers. Putting her energy into what she can control.

“I focused and thought, ‘One point at a time,’ ” she said on court Wednesday after winning in the second round.

"I don't need a Grand Slam to define my career," she told the Associated Press back in June.

She also has said: "I’m intense when I’m out there, but I also realize that life is super short and tomorrow isn’t promised.”

Williams is a player who's a contradiction in many ways—a fierce competitor on the court and a sweet and funny jokester off of it. And she doesn't deny that she wants to win it all, or that the pressure isn't there. "I decided I prefer to have that pressure than the pressure of not winning," she has said. "Not everyone can handle that pressure, but I’m okay with it."

During a Wimbledon press conference in July, Williams threw up her hands, telling reporters she wasn't answering any more questions about the Grand Slam possibility. Afterwards, she told a reporter that it felt good to shut down the questioning. "When you talk about it every time, you can't help but think about it. It's been okay to free my brain from that," she said. "I like that mute button."

Her technique partly comes from recognizing what happens when she succumbs to the pressure. In 2014, she has said, she got so focused on breaking and meeting records that her game suffered, not making the final rounds at the Australian Open, the French Open or Wimbledon. She changed her approach at the U.S. Open, focusing instead on getting only to the quarterfinals. As the New York Times described it in a recent cover story, "she learned not to look ahead too much by looking ahead."

And yet Williams has been described as wanting "to win more than anyone who had ever played any organized game." She recently admitted she always wanted to win the Grand Slam, and that she wanted to do it in New York. She's called herself "the most passionate person you'll ever meet," and that tennis is "more than my job; it's my life. It's my career. It's me."

One need look no further than what she did after a challenging second-round match on Wednesday, when she defeated Kiki Bertens, but only after trailing 3-5 in the first set and coming back from a 0-4 deficit in a tiebreaker. Immediately after the hour and a half long match, she went and practiced for an hour more. That's the mark of a focused competitor, and someone who wants to win it all.

Read also:

How women's tennis fought for equal pay

Serena Williams has finally decided what she wants out of life: Everything

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